Italy trip (cinque Terre ,Florence and venice

You could avoid that long transfer between Cinque Terre and Venice by putting Florence in between them.

Head straight to Cinque Terre first, then Florence, then Venice, returning to Florence the night before your flight.

With 2 weeks you have time for another stop, depending on your interests. Someplace between Florence and Venice would keep the travel distances low. Maybe Bologna, with a daytrip to Ravenna to see the amazing mosaics? Or Verona (;possible daytrip to Lago dinGarda). Even Varenna on Lake Como, via Milan. All easy by train.

Keep in mind that CT will be very crowded during the day, especially the trains between cities. You can split the travel time by going from CT to Milan but really you should just bite the bullet and take the 6-hour train ride. Based on the type of ticket you purchase you could even plan to stop for lunch in Verona, then hop back on the next train to Venice. I would not rent a car as the train service will be much easier and more efficient. Plus, no place to park really in CT or Venice and Florence is just dying for tourists to travel in the restricted zones so you can get a hefty fine. Spend no more than 2 days in CT, 3 days in Venice and the remainder in Florence. Keep in mind that the days in each city do not consider the travel days involved.

Day 1 - Fly to Florence
Day 2 - 5 Florence
Day 6 - Train to CT (stop in Pisa for that tower thing and lunch)
Day 7 - 8 CT
Day 9 - Train to Venice
Day 10 - 12 Venice
Day 13 - Train to Florence
Day 14 - Fly home

I would do:

Day 1- 8 Florence and Tuscany: 7 days
Dévote at least 3 full days to Florence
and the rest to Lucca, San Gimignano and Siena
Day 8-10: Cinque Terre - short stop in Pisa to see leaning tower, Cathedral and battistero
Day 10: return to Florence around noon take high speed train to Venice - arriving Venice in the evening - dinner on Piazza San Marco
Day 11-13 -sightseeing Venice - leave Venice to around 4pm
stroll around Florence and dine in the centre or Oltrarno.
Day 14 return home

The Homo Faber exhibition will be happening while you are in Venice. Showcases the finest of the world’s craftsmanship. Not to be missed, which is why our next trip is scheduled around that exhibition.

There are also buses from Florence going to CT every morning around 7 am
and returning in Florence in the evening
https://www.ciaoflorence.it/en/tour-detail/12
The boat trip is worth it.

Is it too late to plan the trip so you fly into Florence and out of Venice ( or the reverse) to avoid the backtracking?

I would also recommend you:
https://florencewithflair.com/custom-tour-florence/

Thank you all for your insights.
I like the itinerary franciose posted ( tuscany is a must too)
Clarification about driving and parking very helpful.
Unfortunately , i do not think i can change departure flight, but will give it a try.
Thanks for the tip on the craft festival in Venice !

Lisa