Zoos are places in which captive wild animals live, for humans to watch and study. People in a zombie attack are most likely going to stay away from a zoo, so save for a few die-hard zoo employees, zoos are likely to be largely deserted in the event of an apocalypse.
1. Some animals could be domesticated for personal use, although most animals will be dangerous.
2. Food sellers are located around zoos so there are supplies.
3. Most zoos will have large envrioment for the animals that are meant to keep people out.
4. Most zoos will have their own generators for some of the exhibits.
5. Zoos are usually surrounded by high walls or fences, and they are large, easy-to-defend pieces of land. Many zoos are capable of being easily fortified with items already inside the zoo such as buses, railings, benches etc.
6. Animals may serve as a valuable early warning system against approaching zombies, and might even mask the smell and sound of humans, making a zoo uninteresting to zombies passing by (although this could backfire if the animals inadvertently alert the zombies to live prey and they eat animals as well).
7. A suitably remote zoo with enough space can easily be used to sustain several families quite safely, with agriculture and livestock being utilized and produced.
1. Animals are most likely going to go feral and starve unless you spend an enormous amount of time sourcing food for them. This effort is better spent looking after yourself. Allowing the animals to roam free will pose a safety risk to you and other humans.
2. Many zoos are in densely populated areas, so they may be surrounded by hundreds of thousands of G's. This is an untenable long-term situation.
3. The wild animals in the zoo were left to survive on their own, so they go feral. Thus, It is better to keep away from these large, dangerous animals for our own benefit.