That´s awesome to do, kiwibuddy!!!
I´ve once recreated the Jurassic Park experience by leaving only a few guests inside and then building a wall in the entrance, to prevent people of getting in.
Then , i use the "The Rock" cheat to crumble any buildings to dust and **** of the big lizards.
Delete only a piece of fence of every enclosure to release the ****** off reptiles. Awesome results; especially when you have a zoo divided in Islands and if the main island is filled with dense forests, massive rocks, lagoons, rivers and T-Rexes, Spinosaurus, Allosaurus and Raptors roaming the forests and the now-ruined facilities. Ah, and don´t forget to release crocs, deinosuchus and plesiosaurs in the rivers and lagoons.
Have fun, it´s a cool way to do some good chaos.
Also, i made the Raccoon City Zoo once. Just guess what happened with hyenas, lions, crocs and elephants running on the loose in the Small City Map.
Just like Ian Malcolm said: "First, it´s Oooh, Ahh and then, comes the Screaming."