Not sure what Kaido says after the attack in the raws, maybe somebody can help with that. Depending on it you can infer the meaning. If Kaido simply asks does Zoro have CoC? It means that he felt some burst of CoC like when he first fought Luffy. If Kaido asks is Zoro using CoC (like how its referenced later for CoC coating? It means that Kaido is simply surprised by the power of the attack and expects that only ACoC attacks are capable of such a feat.
From my understanding of the context and Kaido's conversation with Luffy which happens immediately after this it would be safe to assume that Kaido was not talking about ACoC, he was simply surprised by the power of the attack and some unintentional leak. Considering that Zoro was in a way worse condition just before Asura than Luffy after getting back up, Kaido would not make the remark of a handful of the very strongest, not a dead man walking.
It is actually one of those character moments that people have been crying for Zoro (or mocking) that has gone unappreciated. Mostly people are stuck on powerscaling the attack for different agendas (mostly coping that it is ACoC) that they miss the narrative point of it. Since becoming a SH Zoro's ambition and dream has taken sort of a backseat biggest example of which is his bowing his head to Kuma for sparing Luffy's life and to Mihawk for training him for Luffy's and the crews sake. Even at the RT he has mostly been trying to protect his captain and his ambition to cut the so called toughest is frequently being pushed behind to the extent that he has to defend against the strongest attack and heavily injuring himself before he can really test himself.
The Asura situation is such that it gives Zoro one of those chances where his personal ambition somehow coincides with protecting his captain and I would say that when Zoro cut Kaido there was an unintentional leak of CoC which Kaido felt. This thread is then followed up in his next fight and Enma has a big role in it and the Kozaburo flashback. Zoro finally accepts (remembers) his ambition, Enma forces him to accept it (Zoro can only have Enma as a sword if Zoro is worthy of it, similar to how Zoro demands standards from Luffy). And part of his ambition during the raid is also fulfilled in this acceptance of his ambitions. Zoro came to cut the toughest creature in the world, his doubt and non acceptance of his ambition resulted in him unable to fulfill his goal, he failed to put Kaido down as he wished. But after accepting his own self, remembering his ambition and realization he did something greater, he obliterated a guy who was even tougher than Kaido. Hard as it is for some to accept, the main reason for King being harder to damage than Kaido was for the character growth of Zoro.
I think that Oda intentionally left out some of the plot lines (Nidai, Ryuma Grave etc.) because they are to be covered later. Though I believe that there is avery high possibility that Zoro will not get Nidai and the current three will be his final swords. Wado is like that partner/lover who will always stay with you and accept you for whoever you are, Enma is the best friend type who will demand the very best from you and Sandai is Zoro himself, his soul, setting on the main journey each testing themselves against the other, relatively ordinary but with the greatest of raw ambitions.
