Sport & Leisure
There are actually 3 Zoos: http://saopaulo.angloinfo.com/search/afsearch.asp?q=zoo&r1=
Info with full contact information is included in the listings.
I have been living here since I was born, kind of 5 decades ago (!), so trust me, the "official " zoo for paulistanos is the one on Avenida Miguel Stefano (maybe I am mistaken with the name, but you have the Anglo Forum link already), as mentioned before. The other one was the so called Simba Safari, before they renamed it a short time ago, and people say it's quite interesting too.
Pet zoo is a "mini farm" visited by schools during the week and very young kids with their parents on weekends. It's a place for urban kids to have their first contact with chickens, pigs, goats, lambs and other animals.
You can get their by public transport if needed: http://www.zoologico.com.br/pagina.php?p=visitas&id=128
Email or post here if you need help with translation.