This again is an unnatural circumstance, but there are trade-offs and there are mitigating circumstances as well. There are situations where animals occur in environments under such stress, they are near extinction. To rescue them and create a special but artificial habitat to preserve them as species is a blessing. And if in the process, they are in a zoo-type setting and many people come to observe and marvel at their uniqueness, that is a benefit for human that is useful. The education of the young about animals is greatly enhanced by direct exposure to the living creatures because they will be perceiving them energetically as well and much can be learned by this. Ironically, children will know if the animals are happy or not and so this behooves the institutions to clean up their act, so to speak, and provide top-notch care for their charges to keep them as happy and content as possible under somewhat artificial and difficult circumstances compared to their instinctive behavior and natural desire to be free.
It is, at best, an ethical compromise to house animals in zoos for public display and, at worst, can be a form of torture if the animals are ill-cared for, including not only inadequate diet, but cramped quarters or cruelty, either in the direct handling and treatment by zoo staff members, or exposure to extremes of heat and cold in poorly designed facilities or periodic shortages of drinking water and irregular meals that may also be of poor nutritional quality for the species in question. These are all a worsening of conditions that will add to the negative karmic burden for those involved in exploiting animals for their personal gain by putting them on display.