is it possible to visit both in same day, visiting cinque terre for 4 five days then pisa for two, so would possibly travel from pisa?
Visiting both in one day will be a challenge. There are train runs that go from Pisa to Siena. The train station is about 1km from the city wall but there are usually buses to meet the train that will take you to the city wall. Then, you can take either the train or the SITA Corse Rapide non-stop express bus to Florence. The SITA bus station is about 1,000' from the main Florence train station. From the main Florence train station, you can return to Pisa. Expect close to 6.0hrs on the train/bus (including train station time).
I might suggest just one day in Pisa and an extra day in either Florence or Siena. My wife and I walked around Pisa a bit and we didn't see anything great except the leaning tower and historical grounds which took us about 90 minutes.
Took the regular train from Rome (noon) to Pisa then another train to Florence (got to hotel at around 8:00PM), all on the same day. Stop in Pisa was only for a few hours, enough to take the bus to Campo di Miracoli, vist the cathedral, view the tower and see the grounds. Two days in Pisa is probably overkill. Florence and Siena were more interesting. Definitely recommend more time in Florence. Happy trip.
thanx both