Kathy covered many of the suggestions I would have made. With such a very short time in Florence, plus the aspect of getting over jet lag, I don't think you have time to take day trips to both the Cinque Terre and Tuscany, which is large area with lots of possible sightseeing destinations.
I can tell you from personal experience that a day trip to the Cinque Terre from Florence is a long and tiring day. Therefore a visit to Siena might be a better option, as you can get there relatively quickly using either bus or train. The bus is often a better option as it drops passengers in the main part of town, rather than at the bottom of the hill where the rail station is located.
Also as mentioned above, there's lots to see in Florence so you may not have time for many day trips. You may want to buy a copy of the current RS Italy guidebook so that you can figure out sightseeing options that appeal to you.
One other thing that occurred to me is that it might be a better use of your time to skip Montreaux and use the extra day in Florence. Staying one night is often not worthwhile as it only allows a few nights for sightseeing, once the transportation times are taken into account.