So which Zoo's exactly did you visit again?
Personally I would just do one or two zoo's, and do lots of animal encounters.
From 1986-88 I lived in Bunbury, Western Australia, and visited Perth Zoo and 3 other minor wildlife attractions. In 2007 my wife and I spent 6 weeks travelling all over Australia for our honeymoon, and we visited 14 attractions. In hindsight I actually wish that we had been to many more, as this past summer we toured 50 zoos/aquariums in 50 days across the U.S.A.
Taronga Zoo - Sydney area
Sydney Wildlife World - Sydney
Sydney Aquarium - Sydney
Melbourne Zoo - Melbourne area
Healesville Sanctuary - Melbourne
Phillip Island Wildlife Park - Melbourne
Melbourne Aquarium - Melbourne
Adelaide Zoo - Adelaide
Monarto Zoo - Adelaide
Cleland Wildlife Park - Adelaide
Warrawong Wildlife Sanctuary - Adelaide
Crocodylus Park - Darwin
Kuranda’s RainForeStation - Cairns
Alice Springs Desert Park - Alice Springs