1: Zoroark is far from the uncounterable catch-all against Annihilape teams. When making an Annihilape team, you plan around this thing. Sure, it completely walls standard Annihilape set, but walling one of your pokemon doesn't make the matchup unwinnable, especially on something as frail and prediction reliant as Zoroark.
2: You may have been using Zoroark on your HO team, good for you. However, just statistically, most people ARE NOT. If you look at the usage stats, you will see that there among the qualified playerbase, Zoroark-H is just barely making the cutoff for OU, and many more standard HO picks like Glim, Volc, Ace, Moth, Bax, Ceru, Pult, etc etc etc are all not only making it, but thriving. It's a mon that only appears on 4.7% of teams, the style of which you already have a disadvantages against and would need to plan around when using the Ape, don't forget. Meanwhile, balance and Stall are doing a lot better in the tier, as evidenced by Skeledirge, Clodsire, Pex, Ting-Lu, Corv's places in the tier, all higher than it.