I'm guessing the other one will be Duke, and that isn't truly a zoo, either. AZA doesn't even consider them zoos. By the broadest definitions, sure, but when it comes to what the general person means by "zoo", and what a list like this should be about? No. I imagine both of those facilities would also say they aren't zoos, as well.
Having large yards and good breeding programs doesn't make somewhere "must see", especially given the large amount of options this country has. If something is going to be "must see", it should be accessible to those wanting to see it.
Disney, SW, and SD have a lot more to offer and are places people will spend all day at, without even mentioning rides and non-animal stuff. They also are considerably cheaper. White Oak is 6.5x more expensive than a full price ticket to either of the San Diego parks. I'm not sure there's anyone on here who would pay that much to go to White Oak, frankly.
Dukes tours are 14 bucks though. So not comparable as Duke is much more accessible. Covid has messed up the tours a bit, but before covid I went on a free-educational tour and was able to see most the species and even the nocturnal building. Everyone is able to make a list such as this and to be honest Duke would be on my list, but its accessibility is less in debate as much as what constitutes a “zoo.”