Italy and Switzerland Trip

Fly into Rome and out of Zurich. To get from Florence to Grindelwald, you can:

1) fly from Florence to Zurich (1hr15min), then take the train about 3 hours
2) take the train in about 10 hours
3) take the train, but stop somewhere lovely overnight along the way. I suggest Stresa.

I'd have to spend some time working on details, but a few thoughts come to mind....

• I don't know what flight options you have from Australia, but you could consider flying inbound to Naples (would probably require a connection at a hub airport such as FRA). From there take the airport shuttle to Sorrento (about an hour - https://www.curreriviaggi.it/ ).
• While Sorrento is not "officially" part of the Amalfi Coast, it's basically the same and it would be a great place to recover from jet lag and get used to being in Italy. It's also a good home base, and easy to take day trips to Pompeii, Positano, Capri or other locations in that area.
• After Sorrento take the train back to Naples ( https://www.eavsrl.it/web/campania-express-en ), and then connect with the high speed train to Rome. Allow lots of time for touring in Rome as there's lots to see! You might consider hiring a local guide to visit sites that are of most interest to you.
• After Rome take the high speed train to Florence. That's a great home base for touring around Tuscany and you can easily take day trips from there to Siena, Lucca or other locations.
• After Florence, you might consider a short stop in Milan (two nights?) and take a day trip to Varenna on Lake Como (about one hour by train each way). OR.... you could spend a night or two in Stresa on Lake Maggiore. The main reason for the extra stop is to break up the longer trip to Switzerland. However, if you don't mind a longer train journey (~6.5 hours with at least two changes), you can skip the intermediate stop and go directly from Florence to Switzerland.
• For your first stop in Switzerland, you might consider Lucerne. It's a beautiful city and while there you can visit Mt. Pilatus or other nearby sites.
• You might consider other locations in the Berner Oberland besides Grindelwald. Have a look at Lauterbrunnen, Mürren or Wengen for places to use as a home base. Most of us here have a preference and I tend to prefer Lauterbrunnen as it's the transportation hub for the area, and provides good access to both sides of the valley. Mürren is also popular as it's a beautiful smaller village up in the Alps. From there it's easy to travel to the famous Schilthorn where the James Bond movie On Her Majesty's Secret Service was filmed many years ago (the only JB movie with the Australian actor George Lazenby).
• At the end of your trip, you could travel by train to Zürich and connect with your outbound flight there. You could spend a night or two there to have a quick look at the city. If you stay right in Zürich, it's only about ten minutes by train to the airport.

A few other thoughts.....
- As you've got lots of time, you might find it helpful to get the Rick Steves Italy and Switzerland guidebooks. They're also available as E-Books and can be downloaded easily in several formats. If you're travelling with an iPad or whatever, that's another option. The books have information on hotels, transportation, local guides, etc.
- If you haven't travelled in Italy before, be sure to do some research on using the trains and other public transport. Hefty fines can result for those who aren't aware of the rules.
- Allow lots of room in your budget for Switzerland, as it's an expensive place to travel (but well worth it, IMHO). You might find that one of the Swiss Rail passes will save you some money. Here's a short description - https://www.ricksteves.com/travel-tips/transportation/trains/switzerland-rail-passes .

Good luck with your planning!

I suggest you start in Switzerland and end in Rome, as it will likely have the best options for flights home.

Switzerland- Florence- Amalfi Coast-Rome

Basically ,move north to south as September moves into Autumn