Agreed on the spacing issues at LPZ. I've noticed the hoofstock yard especially is guilty of that (you mentioned the male Grevy's Zebra, the Sichuan Takins have access to two yards, and I think camels and ostriches have access to two yards as well. I just went to Brookfield for the first time in 24 years a few weeks ago and I saw first-hand how depressed some of it looks. I think people assume that, because they charge for parking and entry, they can afford more, but that's clearly not the case.
The hoofstock area includes Grevy's Zebra, Sichuan Takin, Ostrich, Red Kangaroo, Bactrian Camel, Chocoan Peccary and (according to their website at least) Patagonian Cavy, which I did see once but there's no signage anymore.
As for koalas, I think the reason Lincoln Park Zoo never got any new ones after the last one died around 2003-2004 was because they're apparently a pain to care for in captivity (or at least they used to be). I was reading former zoo director Dr. Lester Fisher's memoirs about the zoo and he said the koalas would change their mind every day about what type of eucalyptus they wanted, and (at the time at least) there were only certain states that grew eucalyptus, none of which were near Chicago.
I do wish I knew what happened to the rock hyrax (it used to share the exhibit with the klipspringers), as it only lasted about a year or so, from what I remember.
