Seeking help on 6 week final itinerary to New Zealand, Australia, and Fiji

Coming all the way from LA for just 6 weeks, I would skip Fiji. Your itinerary for ANZ, while looks ok seems quite superficial and you are missing some of the best bits.
From Auckland, Waiheke is worth a night, Bay of Islands are better than Hahei, or you could visit on the way to Bay of Islands. For me Rotorua was underwhelming but you should at least visit for 1 night not 2. 2 nights in Mt Cook in May - no. A day trip would be better and you may not get a night sky due to cloud cover. I am no expert on NZ having only visited 3 times but I would look at the South Island harder and get more advice.

3 Days Sydney is not nearly enough, especially if you are including a day tour to the Blue mountains. Try to make the time to drive there and stay at least overnight. The tours with zoo visit are not recommended by people who know better. Coogee to Bondi is good, also do a ferry to Manly and take other ferry trips if you have time. Maybe your friends could meet you in Sydney, The South Coast is far more picturesque than north to Newcastle.

Melbourne is worth a visit, not just an airport from which to drive the GOR. Lorne to Apollo Bay is just an hour with not much in between, no need to stay at both. If you want to do some of the walks/hikes in the Grampians, one night at Halls Gap is not enough.
A couple of websites to visit: www.visitvictoria.com & www.visitnsw.com

Are you staying in Port Douglas or Cairns? I wouldn't bother coming back to stay in Cairns if just for the airport next day. Have you looked at Palm Cove?

Hi Brad.
I'm an Aussie we just did a 3 week North Island NZ trip back in May. We did a 3 week South Island trip last May.
On day 6 you are moving from. Rotorua to go just down the road to Taupo then dropping off the rental and catching a plane from there next day. Is that locked in? Seems like a bit of a hassle to change accommodation. Rotorua is the biggest tourist destination on the North Island so I am sure car rental depots and flights are plentiful.
Regardless of that on the road between Rotorua and Taupo (20-25 kms) is Rainbow Mountain. Nice hiking good flora and fauna. Just beyond there is a bumpy couple of kms of dirt road that takes you to Kerosene Creek. A bit of a highlight for us. Lovely bush setting with a flowing 35+ deg C creek with pools and rapids to soak in. Only about a dozen people there when we visited.
Huka Falls could be just a daytrip from Rotorua if you feel it is important. We stopped briefly on our way to Tongariro NP after a morning at Craters of The Moon. It was jam packed so we didn't hang around. I've been there before.
Christchurch to Tekapo.
We stopped a night in Geraldine which is a nice little town, we prefer to restrict actual driving time to around 2 hrs. Geraldine worth at least a leg stretch. It does have some museums and a lovely chunk of forest. There is a brilliant coffee/toilet stop on the highway near Fairlie (I think it is Burke's Pass). You can't miss it,all sorts of unusual things. Worth taking a break there.
Lake Tekapo. You will be too late for the lupins I think. It is a beautiful setting but a rainy day and 8 massive tour buses arriving put us off so we rolled on to Lake Pukaki and Twizel.
You say you are staying at Mt Cook. There aren't a lot of options within the village. We were happy to stay in Twizel, more choice, more services. It meant having to drive one of the World's most spectacular stretches of road twice a day to visit the NP hardly a hardship.
Plenty of hike options in the NP. Lesser known but very good views is Red Tarns hike. A tough little climb views to die for. Only one other hiker when we did it.
Tasman Valley is less popular than Hooker Valley. We hiked alone to the river mouth. Huge iceberg in the lake great views, we hiked back along a ridge above the lake in the company of a very friendly NZ falcon.
We overnighted at Omarama. Worth visiting the clay cliffs there. Doesn't sound exciting but it was quite exceptional.
We didn't visit Wanaka until on our way back north so you will be doing the Crown Range road in the opposite direction. There is a brilliant spot that provides a great overview of Qtown. It's a big car parking space. The road after that has some pretty tight bends, it's a fun drive.
If you have time detour to the old gold town of Arrowtown. You won't be the only tourists there but it is as cute as a button and has good historic buildings and a fun museum (in the old bank from memory).
We loved Te Anau. The drive along Lake Wakitipu with the Remarkables on your left is impressive.
We chose to do coach and cruise tours of both Doubtful Sound and Milford Sound. Both long days but absolute highlights. The less commercial Doubtful Sound was THE highlight of our 3 weeks in the South Island.
You don't say whether you plan to do Milford independently or as an organised tour. We are typically independent travellers but I was glad we chose to do the day tour.
There is also a glow worm cruise available on Lake Te Anau. Also in Te Anau is a tiny volunteer run bird sanctuary. We were able to see a pair of Takahe, very special for me might not be for you.

Great Ocen Road. No need to move accommodation between Lorne and Apollo Bay I'd suggest 2 nights in one of them. Lots of good walking near Lorne, lovely waterfalls.
If you are only staying one night in Halls Gap then maybe hike The Pinnacle. If you don't mind a bit of steep stuff you can start it right behind the caravan park in town.

Looking at your plans it does look a bit of hammerfest with lots of long drives and a number of plane trips covering huge distances in a short time. Obviously that is your call. Not my place to tell you how to travel.

I’m interested to see you are going to Whitebridge - my daughter lives there :)
Just thought I’d mention as an alternative, it’s easy to catch a train from Sydney to Newcastle if you are staying with friends and don’t need a car while you are there. It only costs about $AUD10 per person and runs frequently.

We are staying in Mt Cook at the Alpine Lodge next week, so I’ll try to remember to comment further when we return. Quite a few years ago, we did an overnight cruise on Doubtful Sound - that was spectacular if you get the opportunity.

All of this advice is REALLY helpful and appreciated. I am very close to beginning the process of booking….and so a great time to reconsider and adjust.
My "Day 1" in Auckland is NOT arrival day. We arrive mid day on day prior...so this Day 1 is a full day to recoup as see what we are up for... then renting and leaving city the second morning.
Any suggestions for such a day in Auckland?
From Auckland, had chosen Hahei over Waiheke knowing a majority may choose Waiheke...but we wanted to get some of the ragged coast... seems like Hahei / Cathedral Cove would fit ...then driving a little further to Waihi before turning inland to Rotorua / Taupo. (I understand the Hot Beach may not be that amazing... but hope Cathedral Cove will offer something like rugged N. California coast.)
I had planned on flying from Rotorua to Chritchurch...for all the reasons noted... likely more acceptable car drop off... more and direct flights... BUT then found challenge... I really want to visit Artic Center next to Christchurch airport as one thing to do before end of that day...and it really deserves 2.5 hrs or more to do well...and it closes at 4:30...and only direct flight got in at 2:10... then found car rental accepted Taupo drop off... flight arrived at 1:25... so although indirect.....seemed to fit....BUT I may rethink that as from what I read I could get to Artic center quickly and get in a couple hours. I had planned to go Hahei to Taupo for one night (looks beautiful) ...enjoy same set of sites next day en route to Rotorua that I would have other way (Huka, Aratiatia Rapids, Orakei Korako Geothermal Park & Cave , Wai-O-Tapu). That saves round trip from Rotorua.
For the Great Ocean Road ….tried to take account of time for Otway Park, sunset, ad it seemed lik we had time to have one night at Halls Gap…and therefore could head that route rather than straight back down coast (although that would not be so back ). More on that plan below. Any thoughts for those familiar really appreciated. (We don't mind changing hotels on this route because it saves backtracking).

May 10 - Fly Newcastle (NTL) to Melbourne (MEL) (2 hr) / Rent car and begin Great Ocean Drive / Stay: Lorne (That is as far as we would reach before dark)
May 11 – Great Otway National Park / Reach and stay in Apollo Bay
May 12 – Otway Park > 12 Apostles / Reach and stay in Pt. Campbell
May 13 – Sunrise 12 Apostles; Drive to Hall’s Gap (2.5hrs + stops) / Afternoon hikes / Stay in Halls Gap
May 14 – Morning hike / afternoon drive to & stay in Melbourne

Your first weekend on the Coromandel is the end of the school holidays so accommodation may book up fast. I would tend to take the direct flight to Christchurch myself but flying through Auckland will give you more time as long as the flight is on time. The domestic airport is small but I think the gates are at opposite ends and you have to go through security again. (Haven’t done this for a long time so might have changed now) The line usually moves fast. Sitting on the left side of the plane gives you more chance of views out the window. The Antarctic centre is basically on the airport grounds.

We loved the Tiritiri Matangi nature preserve which is accessed by a boat from Auckland.

Re GOR: I think you could eliminate one night. We stayed in Lorne, Port Campbell and Halls Gap and had plenty of time for walks along the way. You could visit the Healesville Sanctuary near Melbourne and drive to Philip Island. We went to the Penguin Parade that night and stayed about 20 minutes away. The next morning we began the GOR drive. In Halls Gap, we stayed at HG Lakeside Tourist Park. It's not fancy, it's an RV park with 'cabins' to rent. It's next to a large field you can walk to to visit with the kangaroos, emus, and cockatoos, especially late afternoon. We are from LA and honestly the Grampians are nice but nothing like the Sierras. We enjoyed stopping at the J Ward Museum on the way back to Melbourne. We also stopped at Tower Hill on the way to Halls Gap and saw emus and koalas in the parking area.

I am only going to comment briefly on the NZ part in general. I spent 5 weeks there in Jan/Feb this year so my weather was different. I wouldn’t disagree on any of your stops, nor would I say to add more. You may have perfect weather, but you will need to be prepared to pivot if you don’t because for several places you haven’t left any room for bad weather.

I wouldn’t quibble about the Coromandel but it’s not a fast drive to get in and out (although gorgeous). I didn’t make it to Cathedral Cove because of weather - not rain every day, but wind, although the weather was nice enough. If it’s raining a lot, I would skip,for,somewhere else. Same with Mt.Cook - keep an eye on weather and be ready to change your plan if necessary.

I also understand the difficulty of flight times and car returns, but the drive isn’t far between Rotorua and Taupo.

If you do Facebook, there’s a really good group called New Zealand Travel Tips that has tons of information.

Edit even though I said I was only talking about NZ. Lol.
Healesville Sanctuary is great if you are wanting to experience Australia’s unique animals.
I wouldn’t drive to Phillip Island unless you are staying very nearby afterwards (also check time of year and penguin population).
And if you are interested in wildlife and near Warrnambool, one of the most fun sanctuaries I went to was Warrnambool Wildlife Encounters.

The arctic center is very close to the Christchurch airport. The airport is small and it will take very little time from deplaning to get to the arctic center. It is about a 10 minute walk from the terminal to the Arctic center.

It will take at least 2 hours to drive from Tullamarine (Melbourne airport) to Lorne so your decision to pull up stumps in Lorne on May 10 is sensible.
May 13. So morning visit to the 12 Apostles then head off to Halls Gap? Gives you the afternoon to explore and hike and also next morning before heading to Melbourne. You probably won't see much of Melbourne if that's the case. Personally I am not Melbourne city's biggest fan (born and raised there) so I see no issue with that others will disagree.

I visited Fiji (two ports) while on a transpacific cruise. It was interesting, but didn't knock me out.
Suggest skipping.