I don't know why, but a movie that's so absurdly over-the-top silly bothers me a lot less than something like Kevin James' The Zookeeper, (though both still fall far, far short of Fierce Creatures as best zoo movie). Fans of the classic zombie horror films will enjoy the new take on this movie, laughing as characters make poor life decisions that soon change into life-ending decisions.
For zookeepers themselves, the most fun would be in the speculation of how this movie would have gone if we'd written in. Gorillas? Pshah. Imagine zombie cassowaries? Zombie mambas? Zombie fossas, slipping through the air ducts and dropping down on you? Granted, a lot of keepers I know have a hard time watching movies where the animals die - I know some folks who refused to watch The Walking Dead because of Shiva, the tiger - but this is just so beyond realistic (and the animals are aren't really themselves, after all) that I didn't find this too objectionable.
I think it would have also been more fun if they'd done more with unexpected zombie killer animals. Something about watching a giraffe eat a person is very unnerving and very funny at the same time.
For some reason, I can't upload a trailer. Here's a link to one on Youtube.