You will likely find this excursion mentioned a lot as it’s unique to the Belize stop. It is a neat experience. We did it years ago. Yes it’s about 50 minute drive or longer if you go on the ship tour bus. The tour companies are well aware of when you are due back to the port to get on your ship. Belize is a tender port so it takes a bit longer to get to the port & get back. The ship & the tender crew will tell you the time of the last tender departure back to the ship.
As to the Zoo, I think it is even farther away than an hour’s drive.