It's seems like I have to make separate threads about Advanced Armament Haki and the difference between brawler's and swordsman's CoA.
So basically, at the beginning of timeskip, Zoro have normal Armament and it could possibly be better than Luffy's in Fishman Island. And then when Zoro's trying to tame Enma, it sucks his haki off but he's immediately restrained it. He say that he'll get even stronger because his haki will get improved if he manage to control Enma. During the beginning of the raid, Zoro's slashing some fodders with Enma which indicates that he got used to it and now against Kaido, he couldn't cut Kaido because he wasn't releasing enough haki. And you clearly need Advanced Armament in order to hurt Kaido according to Hyogoro. So my guess is that Zoro learned Barrier Haki (which is why I wanted to make a thread about brawler's and swordsman's CoA) after he finished his training with Enma but he is not yet to learned Penetration Haki which is similar to like Observation Haki with sensing presence and predicting movement. Barrier Haki is for swordsman like the Scabbards and Zoro while Penetration Haki is for brawlers like Luffy and Hyogoro.