Hope this reply is not so far downstream from the time you asked that it is now irrelevant, but if I understand your question, it is are zoos inherently good or bad?
I do not believe they are inherently bad, but until quite recently, most zoos were found a great deal lacking when it came to housing for the larger animals and only marginally good for smaller ones. If we are to keep animals in an enclosure, it should be one that allows them a reasonably large enough space for them to roam around without losing their minds trying to find solitude. In addition, many large zoos are found in climates that are nowhere near like the natural habitat the animals come from, therefore, nothing like a natural setting. Children love to see the animals, but have no knowledge of the impact of the enclosure.
Some zoos, such as the San Diego zoo have space enough for many animals to live as they would in the wild, but I doubt any zoo really has space to allow this setting for really large animals such as elephants, giraffes, rhinos and such. On top of this problem, enclosed animals seem to tend to be more dangerous to themselves if they are territorial and have too many specimen in the same area. An example is the death of a giraffe in the Little Rock from falling during a fight with another younger male giraffe. Add to these problems the seriously minimal funding most zoos receive from state and local funding and you have a recipe for disastrous situations for all of the animals.
I enjoyed visiting the aquariums in Chicago when I was a small youngster, but seeing them now, I wonder if that is even a good thing.
Are zoos good, probably not, but for those animals that have lived all their lives in a zoo, it is the only place they can live now, and it may be the only hope for some animals that are eminent danger of extinction from poaching as well...neither of these situations is desirable, but it may be a matter of accepting the least offensive solution.