I was wondering, since the male elephant in zoos is mostly separated from the herd, does that work out in a bit larger exhibit with cheetah/hyena/african wild dog?
Elephants and wild dogs were some of my favorite mixes as a little kid playing ZT2 (mostly just cause they're two of my favorite animals), but I think it'd be a disaster waiting to happen IRL, whether it be with a herd of super protective females or a hormonal bull (not to mention I've heard of AWDs in the wild trying to nip the tails of elephants as a play behavior, which I doubt would go over well in an enclosed setting). Considering how often spotted hyenas prey on small/young/sick/etc elephants in the wild I'd imagine they'd be among the quickest to spark an aggressive response, and the poor cheetahs would probably be very stressed with how skittish they are (not that all of these animals wouldn't be stressed in the mix, but y'know). I think one of the other, smaller, less social hyena species would be the safest bet of those options, but I still wouldn't risk anything, mostly for their sake.
Of course, none of those more species-level behaviors matter in PZ. AFAIK no animal can kill a full-grown elephant in-game besides another elephant (unsure if the calves are a different story or not). Where the trouble comes in with this mix is that most of the game's predators will get spooked/intimidated by XL herbivores, which I think will increase their stress stat - though I don't think the herbivores will go as far as to attack them in my experience. It might work if you built a massive exhibit where they aren't forced close to each other all the time, especially if the carnivores can de-stress in a sectioned-off area of the habitat that the elephants are too big to access. Alternatively, I think you can just turn off intimidation entirely if playing sandbox.
Speaking of cool elephant mixes though, I've seen guineafowl/impala/Thomson's gazelle/elephant and giraffe/zebra/ostrich/elephant mixed pretty successfully IRL, though all with female elephants. Though I've also heard of baboons being successfully mixed as well as cape buffalo and eland. That said, every (successful) exhibit I've heard of with elephants and other large and/or medium herbivores has been very,
very large to allow the animals space away from each other (Borås Zoo and Dallas zoo's savannas come to mind).
All I'll ever dream of for this game is getting to mix my elephant herds with guineafowl and crowned cranes. ;-;