There is a difference between a Zoo and Mefou National Park. That is one way to understate it...
Mefou National Park is unique, besides being one of the best attractions of Yaounde city. It's a place that is always trying to ensure primates' safety, you will encounter a different world filled with a lot of nature trails and see the best way to protect monkeys, gorillas and chimpanzees is not to put them in a cage.
You are going to be able to interact with them and see how they develop in their correct habitat.