Italy, Switzerland and France

There's a great deal to see in Lyon; I wouldn't want to attempt it as a day trip from Annecy. The train will take 2 hours each way, or more. There's a train at 7:43, then the next one useful for a tourist is at 9:53 AM. The trip to Geneva from Lyon isn't all that much longer than from Annecy, and it doesn't require a transfer. I'd plan to spend the night in Lyon on Day 12 and Day 13. That way, you save a bit of train time, overall.

I don't know that it would help you in any way, but Lausanne and Geneva are very well connected by rail.

I am doubtful about the advisability of heading to Zermatt for just two nights, but you might get lucky with the weather. I suspect the weather's more reliable on the Italian side of the border, but it's not something I've ever researched.

Gastlosen might be difficult--I looked into it a bit when I went to Montreux and it did not seem easy by public transport. Nor did Gruyeres really. But there are other mountain hikes that are quite easy from Montreux. See https://www.montreuxriviera.com/en/G514/panoramic-hikes
I think you need to delve deep into the transport to see if any adjustments need to be made.
There might be somewhere you can stop en route to Zermatt, but that blows up your day trips options. Can you go Turin to Zermatt without passing back through Milan and lakes again for example? I don't know, but these are some possible hiccups I can see after skirting these areas.

Would you guys recommend skipping Zermatt all together and just pop over from...say Lausanne at moments notice if the weather is good? Would Lausanne be a good station for Zermatt as a day trip? I booked my flight and realized that May isn't the best for visiting high alpine altitudes lol...my mistake...

Check train times on the SBB website. I would consider that too far for a day trip. Look up something called Glacier 3000, which is much easier from Montreux.
I know it's really hard planning a trip around weather conditions, but you have many options--good luck! I am no expert, just visited once, but I have read that in May, Lake Geneva area, Lucene area, and Lugano area all good.

^thank you!! I had my heart set on Zermatt so it would be painful to let it slip but Switzerland will always be on my list. I just checked it's a 3 hour ride one way...which I guess is doable, but whether it's worth it is another question! :)

I would not argue strongly to exclude it, as you can't really count on weather--I was in short sleeves at the very end of October, and I was warned about the weather then, too!
But do scope out all of the transport, as I think there might be a more advantageous routing. Perhaps go to Turin first, then go back through Milan, to the lakes, and on to Switzerland from there? I wish I knew of a good source that lists all of the train routes for this area.
And be sure to look at the Montreux hikes, as there is a famous one in spring through blooming narcissus that it would be shame to miss.

I did bookmark the white flowers trail! It looks beautiful!

I'm looking at trains out of Turin and it looks like there aren't that many direct routes....everything goes through Milan, if I go straight to Geneva or Lausanne, it's basically a full day travel. It's starting to look like I need to pick a different city than Turin and just make Turin a day trip from Milan...

Simplified based on train patterns:

• Day 1-3: Milan (3 nights) ***Day trips: Como, Bergamo OR Turin
• Day 4-8: Lausanne (5 nights) ***Day trips based on weather and flexibility: A) Montreaux (+hike) + Chateau de Chillon, B) Gruyeres, C) ZERMATT (I will haul ass to get there if the weather is good), D) Gastlosen
• Day 9-10: Annecy (2 nights)
• Day 11-13: Lyon (3 nights) ***Day trip to Perouges
• Day 14-15:Geneva and fly out (1 night)

Day 3: Day trip to either Bergamo or Venice (been in busy summer) - sleep Milan

That's a long time to be on a train to arrive in Venice with the peak tourist tide - after the beauty of dawn and early morning - and leaving with the tourist tide all the way back on that long train trip to Milan. You'll miss the beauty of Venice in the evening when the magic happens. Maybe you could take a really late train back to Milan and get a ride on a vaporetto down the Grand Canal in the dark with the huge Murano glass chandeliers lit up in the palazzos reflecting in the water. But would you be too late getting back to Milan? It isn't the closest city pair.

Day 2: Day trip to Como - sleep Milan

A day trip to Lake Como can be a nice day, but it takes a while to get there. Waking up to the lake lapping under your room as you wake up and then have breakfast overlooking the lake is special.

If a day trip is all you have time for, that will be better than nothing. I hope you have a great day.

I guess you are fitting a lot in quite tightly. We all travel differently and this would be way too fast for me, but I hope you have a great holiday.

I agree with Nigel that a day trip to Lake Como is doable, but it depends on what you want to see there. I was there in June 2019 and spent the night in Lenno, but with train schedules I really could only see Villa Carlotta, which was pretty but I'm sure is much more beautiful when its many rhododendrons and azaleas are blooming, probably March-April (I'm planning to go in early April 1 night) I also noticed that Villa Carlotta is open daily and Villa Balbianella is closed Mon. Wed., so I'm staying over on Monday night and plan to see Villa C in the afternoon on Monday and Balbianella on Tues. morning before heading back to Milan to then train up to Wengen the following day. It's a bit aggressive, but I like to pack activities into my trips -I think it makes it more memorable. Do check out the lake ferry schedule to research whether a day trip is too complex, they only have the schedule through March 23 posted currently, but the later schedule should have a few more options between ferry stops.

Kathleen the I did BO and Milan last time I was in the area. I stationed out in Lauterbrunnen for a few days and used Milan as airport city and gateway from Switzerland to get to Verona and Venice. I absolutely LOVE the BO area and would go back 110%. I don't think you're packing too much (because I think I'm the same way) especially if you're just taking the train and not driving, although I'm also contemplating just getting a car because of the convenience and flexibility - I also happen to enjoy driving too haha