I agree with others that this is way too much to try to do in one day. Cinque Terra itself deserves more than a couple of hours. As others have also said, it will be extremely crowded, and extremely hot during the day.
I was in Italy in August of 2023, and late morning until late afternoon it was so stifling hot. I was in my early 40s and I love the heat, and this was on a whole other level. Any hiking that I did on the Cinque Terra trails was finished before 930am. One day I started off at 745am, and the other day I started off before 7am for a slightly longer hike. The sun was rising but hidden behind the mountains, keeping the temps manageable. But once that sun came over the peaks and you walked into it, it was already like walking into an oven.
As a family we explored a couple of towns early in the mornings, and stopped to swim off the pier in Vernazza for a while to stay cool before heading back to hang out in the AC and relax before heading out for dinner and a stroll. I could NOT imagine trying to do any sightseeing or hiking in the middle of the day in August. Aside from the heat, the CROWDS were absolutely insane. No room to swing a cat.
If you have time in your itinerary, make CT a separate trip for at least 2 nights to give yourself time outside of the midday heat and crowds. The towns are so much more charming early in the morning and later in the evenings. If you don't have the time, then I recommend that you come back to Italy and make more time for it in the future instead. My family loved it, we had some very memorable dinners, walks and time in the beautiful water or at the beach, and we all hope to return before too long. None of that would have been possible to experience in a couple of hours.
We also did a day trip (from a house in Tuscany) to Pisa and Lucca in one day. This is a more realistic way to spend your time. You can get an early start on the road and get to Lucca nice and early for a wander around town, and then to rent a bike or some 4-seaters and pedal around the perimeter of the old city walls (we and our kids LOVED That, they still talk about it). Grab some lunch in Lucca and then head over to Pisa where you really don't need a lot of time to see the Tower and Duomo. It will be nice and hot by the time you get there, so you will be happy that you don't need to spend TOO much time.