I do not think that it is cruel in any way to put animals in zoos if and only if the animal was 1. injured but brought into a zoo to take care of it then release it back into the wild 2. the animal was born in captivity and is thus unable to survive on its own in the wild 3. the animal's parents were killed when it was young, therefore having no one to look after it 4. the animal's parents deserted the animal or 5. the animal was brought back to study it without means of dissection, in order to better preserve its species' survival.

The animal must of course be kept in an enclosure that is not too small or too crowded. An open enclosure such as the ones in our very own Singapore Zoological Garden would be best

Zak