Switzerland to Italy itinerary advise

I would skip the 3 nights in Zurich and add them to Luzern and Lauterbrunnen. Zurich is a big cosmopolitan city, but not nearly as cool as the other two places. Plenty to do in Luzern.

I think Stan conflates Zurich with Zermatt. Looks fine to me.

There’s quite a bit to see and do in the Lauterbrunnen Valley. If it were me, I would allow five nights not three and remove Lucerne. I think you need to slow down which will make your trip easier.
You can fly nonstop on Swiss airlines from Zurich to Florence but it’s not cheap. Florence deserves three nights not two and buy tickets for the Uffizi Gallery two nights out to guarantee a reservation. There’s a lot to take in here too so don’t short change it.
Why three nights in Sorrento and three in Praiano? Praiano has no ferry service so you won’t be able to take ferries to get around. It would be nice to see the coast from both land and sea. I suggest staying in one spot on the Amalfi Coast and Amalfi would work better than Praiano.
To get from Florence to Amalfi take a direct train from the Firenze S.M. Novella station to Salerno (4h 15m). From Salerno you can take a ferry to Amalfi: https://www.trenitalia.com/en.html and https://www.directferries.com/global/index.html.