Nice shots .. but I have to ask ... does that Zoo let the patrons in with the animals?? Because that's what most of those shots look like .... like you were inside their cage / enclosement. Nicely done.
I'm not sure if this particular zoo allows patrons into the exhibits; I certainly didn't go inside any of the cages or enclosures.
My approach was to head in armed with a 70-200/2.8 and a 300/4. I just stayed at each exhibit, trying different angles, waiting for suitable lighting conditions etc. until I was confident of a decent shot. Sometimes this meant waiting for quite a while e.g. it took 1/2 hr for the Koala just to open it's eyes.
Two of the images (the tiger and the lizard) were shot through a clear perspex panel which made up part of the cage. Getting photos through the clear panels was a little more tricky than I'd originally anticipated. Firstly, you have to find a clean section to shoot through. Mostly the panels are covered with hand and face prints from kids who have been eating ice cream. Secondly, you have to find an angle that doesn't have a reflection e.g. the image below, you can see the reflection on the left hand side... And thirdly, you have to get a nice shot of the animal. Needless to say, there were many images that just didn't work.
A 'photographer package' would probably eliminate many of these difficulties, though I'm not sure I'd get into the cage of a Sumatran tiger...