I have a big group of people around 40 or so is the zoo fun or boring

Depends

Fun to be precise

Fun.

Depends on the age group and the desired experience.

Schools do class trips all the time. I have been part of and seen other large groups attend. It is a very good, large zoo. Boring? No.

Depends on if you have little kids its fun seeing the animals but its a lot of walking it easily can tire out little children