I haven't played the scenario yet, but it sounds hard. I like to try to beat it without cheats which I do. I came up with a strategy but I'm not sure if it works. It's like this...
First, you adopt a dromedary camel, wheeeeee not endangered. But when you get enough zoo fame, release the camel to the wild and replace them with scimitar horned oryx. You can do the same with these animals!
-Peafowl>Giant Panda, Red Panda, Spanish Lynx, (Asian Black Bear?)
-Gazelle>Sable Antelope, Wild Dog, African Elephant
-Bison>Wild Horse
Etc.