Honestly, if you stop and admire everything it’ll take you maybe 1 and a half to 2 hours to go through the whole zoo. Give Galápagos Islands, Texas Wetlands, Birds of the World, Pantanal, Elephants and the African Forest the most priority. As for the other exhibits, the Natural Encounters at the beginning is very skippable unless you want to see a specific species in there (Asian small clawed otter, white faced Saki, sloth, electric eel, prehensile tailed porcupine meerkat) as it’s very much designed for kids and has a rather miscellaneous species list. The reptile house has an excellent collection of herps, but it’s nothing special in terms of exhibitry. If you’re not a reptile person it’s an easy skip. The entire left side of the zoo beyond the elephants is just a boring line of square hoofstock habitats, nothing special again unless you want to see those species. The entire middle area of the zoo labeled “Cats, hoofed animals, and more” is quite confusing to navigate and will require backtracking to see everything. The main events there are the lions, tigers, and black bears with addition species being Komodo dragon, Ankole cattle, cheetah, African painted dogs. The world of primates might as well be a ghost town honestly. All of the small monkeys are gone, replaced with birds, leaving African monkeys, and Asian apes. It’s a mostly outdated exhibit, I wouldn’t recommend visiting it unless the gibbons and siamang are vocalizing. Lastly the children’s zoo, is a little unique, but still not something I’d prioritize. Species here include North American river otters, bobcat, banded mongoose, burrowing owl, leopard tortoise, goats, llamas, and zebu.
If I were you I’d start with the elephants nice and early possibly even as your first exhibit and work your way around the whole zoo clockwise. This way you finish with Galapagos during a time with no keeper talks in the exhibit so you can experience it without much of a crowd.
Additionally, the best time to catch the blue duikers is right at opening. They tend to hide more and eventually retreat to their backstage area the more crowded the zoo gets. The Allen’s Swamp Monkeys rotate with the Red Tailed Monkeys and De Brazza’s Monkeys, so you’re not guaranteed to see them. Hopefully they’re out on your day. I also never have any trouble seeing the Yellow Backed Duikers, if they’re not with the okapi, they’ll be with the bongos.