Not sure how “hot” this one is, but I consider gorillas to be pseudo-pachyderms.
Yes, they are obviously primates, but they are the most pachyderm-like of all primates: they’re large, grey, African, and herbivorous, much like elephants, hippos, and rhinos.
If a zoo doesn’t have “traditional” pachyderms, I think gorillas can fill a similar niche. Como, Franklin Park, and Santa Barbara all lack the “grey giants”, but have gorillas, so they feel like they have pachyderms.
Also, if a zoo has elephants, hippos, rhinos, and gorillas, they are either flexing their acreage or one of those giants is getting the short end of the stick exhibit-wise (Memphis with elephants, Denver with hippos, Cincinnati with… all but gorillas at the moment).