I like fast travel, but this would be too fast even for me.
I agree with the suggestion to leave out Cinque Terre. My suggestion would be:
4/2 - arrive in Florence late afternoon (approx 2:30 pm @airport) - hotel Degli Orafi. Walk around. Get gelato. Figure out the lay of the land.
4/3 - Florence. Depends what you want to see here. Options include the Uffizi Gallery (Boticelli's Birth of Venus, et al), the Accademia Gallery (Statue of David), the Duomo/tower etc., the Pitti Palace and Boboli Gardens (I enjoyed these but would probably skip this if I had such a limited time.) Of course, there's the Ponte Vecchio, but you pretty much can't miss it, and the Piazza di Signoria, which is easy to see as it's in the same general area as the Uffizi gallery and the Duomo.
4/4 - Pisa day trip, plus some time wandering Florence in the evening.
4/5 - high speed train to Rome (time TBD) . Rome sightseeing after you get there. You could walk around and see the Pantheon and Piazza Navona, or the Trevi Fountain and the Spanish Steps, for instance.
4/6 - Rome sightseeing. Colosseum and Palatine Hill, perhaps. Also wander and eat. :)
4/7 -Pompeii / Mt Vesuvius (day trip) --look for a tour to Pompeii and Sorrento with the Roman Guy. We did it, and it was great, albeit to Pompeii and Sorrento. (Note that you see Mt Vesuvius on the way and from Pompeii. If you want to climb it, then you would probably want to do an overnight in the area.) Alternatively, you can take the train to Naples and get to Pompeii from there. Some people say this is faster, but for us, we liked the simplicity of the tour. We also liked getting to spend a few hours in Sorrento--a beautiful town that might help to make up for not seeing Cinque Terra. It IS a long day and a long drive, but if you're prepared for that, it's still worth it, IMO.
4/8 - Rome sightseeing. Vatican and St. Peter's perhaps.
Tours we did in Rome included the Capuchin Crypts (loved), the Appian Way, and the Catacombs (wouldn't do again) with the Roman Guy, and also the Vatican Museums, Sistine Chapel, and St. Peter's Basilica with the Roman Guy.
4/9 - Travel home