Why it is called "Jurassic Park" instead of "Jurassic zoo"?

Jurassic Park not Jurassic Zoo because it's meant to be an amusement park. An amusement park has a lot of attractions, rides, merchandise sale etc. like Disney land.

Here, instead of clowns and cartoon characters, we have dinosaurs, but we also have a lots of attractions and rides.

A lot of these things have been shown in Jurassic Park as well as The Lost World. Visitors to the Jurassic Park not only get to see the animals in the open, but also a short movie about the park's origin, the labs etc. There was a huge plush cafeteria of sorts.

So these things make it a park, rather than a zoo, which is much smaller in its scope.

It probably comes from the distinction between 'zoos' and 'Safari parks'.

Zoos are typically areas with cages in which animals are 'displayed' and the public walk around looking into the cages. So, outside, looking in.

'Safari parks' generally have differing groups of animals in a more natural habit with some freedom to roam and interact. In safari parks, the public usually travel through the park in a car or bus and and therefore inside, looking out.

The way that (parts) of Jurassic 'park' are designed is far more similar to safari parks than zoos.

Besides, 'Jurassic Zoo' would have been a pretty crap name !

Michael Crichton's foreword to the Audiobook version of Jurassic Park specifically addresses this point. The island is intended to be a theme park (e.g. complete with rides and attractions), not just a zoological garden for animals.

"I wrote a screenplay about cloning a pterodactyl from fossil DNA in 1983, but the story wasn’t convincing. I worked on it for several years since, trying to make it more credible. Finally I decided on a theme park setting, and wrote a novel from the point of view of a young boy who was present when the dinosaurs escaped. I then sent the book to the usual people who read my first drafts."

In the source novel, the character John Hammond gives us an insight into his own thinking on the subject:

“Well, Donald,” Hammond said, “to explain that, you have to go back to the initial concept of the resort. The concept of the most advanced amusement park in the world, combining the latest electronic and biological technologies.

As does John Arnold, the park's chief engineer:

“None of the rides are running yet,” Arnold was saying. “We have the jungle River Ride, where the boats follow tracks underwater, and we have the Aviary Lodge Ride, but none of it's operational yet. The park'll open with the basic dinosaur tour - the one that you're about to take in a few minutes. The other rides will come on line six, twelve months after that.”

“Wait a minute,” Grant said. “You're going to have rides? Like an amusement park?”
Arnold said, “This is a zoological park. We have tours of different areas, and we call them rides. That's all.”
Grant frowned. Again he felt troubled. He didn't like the idea of dinosaurs being used for an amusement park.