Switzerland and Italy

. How many days are you planning on Switzerland? I just celebrated my 50th there last month. I splurged and got a 3 day Swiss Travel Pass which turned out to be a good deal. It covers the Bernina Express (except you pay to reserve a seat). You could take the train from Milan to catch the Bernina Express in Tirano
I am not sure if you can buy Swiss Rail passes in Tirano though if choose to try it. Someone here will know.

I was thinking 3 or 4 days in each, Italy and Switzerland

I would go go for the4 day Swiss Travel Pass. I wish I had that extra day. I did Golden Pass Route from Monteux to Interlaken. It is over rated. I stayed in Murren at the Hotel Edelweiss which I recommend.

A lot depends on where you want to start and end. Ideally at the two ends of a sort-of linear path. And, how much time and $ you have (Switzerland is expensive). From the US lots of flights go into Milan, Rome and Zurich so they might make good end points. Sept/Oct are shoulder season, more so up north than down south, but there may be some good opportunities.

Might suggest reversing the order to give you the chance of better weather up north and finishing with more time for driving leisurely along the coast into Tuscany. Getting back to Milan is easy from there, or drive south towards Rome and come back that way.

Zurich - Berner Oberland - Lucerne- Panorama Express [Lake steamer along Lake Lucerne and across the Alps through the Gotthard Pass by train] to Bellinzona - to Lake Como - to Milan - to Genoa to get a car and have your drive into Tuscany.

https://www.sbb.ch/en/home.html

We had a wonderful trip to Switzerland/Italy a few years ago. We flew into Zurich and immediately took the trains to Wengen for three breathtaking days of beauty. Then trains to Stresa, Italy on Lake Maggiore (one of my favorites). Then trains to Florence, Siena, stopped further south, and finished in Rome.

For one week I would choose either Tuscany or Switzerland, three or four days in each is really very little.
Tuscany is very very large, where do you want to go: Lucca, Pisa, Siena, San Gimignano, Etruscan Coast, Pitigliano, Arezzo, Pistoia, Pomarance, Montalcino, Cortona, Volterra, Castiglione della pescaia, Monte Argentario, Tuscan Isles like Elba, Capraia?
In Switzerland? Luzern? Lugano? Ticino? Bern? Lausanne, Geneva? Mont Blanc? Cervino, Lauterbrunen? Will you do some mountain walking? If yes, you might be tired at the end of the day you do it.

Gee, only 8 nights on the ground. That doesn't leave much time. I'd lean toward more time in Italy.

Fly Swiss to Zurich, arriving 10:30 am. By 11:30, you can be in the airport train station and be ready to go. Take a train(s) to Pontresina via Chur, The section from Chur to Pontresina is on the Bernina Express (and the Glacier Express) route. Spend a couple of nights in Pontresina, then take the Bernina Express over the mountains to Tirano, Italy. Then change to a train to Varenna on Lake Como for 2 nights.

Then train to Florence, changing trains in Milan, rent the car and do Tuscany. After 4 nights, fly home on Swiss from Florence connecting in Zurich.

Sam, I like your idea, starting in Zurich and headind south, I would like to avoid as much cold weather as possible . The idea of 2 nights in lake Como sounds fantastic. Thanks for all your advice. I may have to consider 4 nights in Switzerland and 5 nights in Tuscany. I know there is so much to see now i just have to narrow it down