I see zoro letting enma suck out his haki and that brought out zoros CoC and somehow people saying thats better than luffys controlled kings haki yeah i dont think so, these really guys dont like luffy and down play everything he has gone though.
Rayleigh stated that CoC is the embodiment of the willpower of the user itself. The stronger your willpower, the stronger your conqueror's haki gets.
@Kiiro make a good point here. The reason why Zoro suddenly unlocked Adv CoC in such a short amount of time is because he finally embraces his dream of WSS and doesn't talk about Luffy's PK dream all the time. And during his flashback with Kozaburo, he finally understand the concepts of the way of the swords and thus he was able to tamed Enma fully. While I don't necessary agree that Zoro's willpower is greater than Luffy's, it's undeniable that both are in the same caliber.