Yes, they can and this been known to happen, but not usually in 'mainstream' zoo's. But usually places that do help injured or new born wild animals are organisations such as charities thats purpose is to help species to learn how to survive in the wild again, but this may not be specifically for just endangered species, although im sure there are organisations thats purpose is to help endangered species offspring survive in the wild. But sadly the majority of zoo's purpose is to not help species learn how to survive in the wild, but merely for human entertainment!