I mean, Luffy spent 2 years learning to master haki and still hadn’t figured out how to do it and then spent days of someone teaching him. Luffy also used CoC several times without knowing he did it and needed Rayleigh to train him on how to use it.
Zoro used it once without knowing what it was and was already doing it not even an hour after Gaban just told him it was possible and sent him on his way.
He didn't need Rayleigh, Rayleigh chose to teach him and simply sped up the education process. People like Luffy would have figured this thing out eventually. No one told him one could Clad attacks with CoC, he learnt that on his own, Zoro had to be told if you're trying to suggest Zoro is the better. If Zoro were, he'd have known this without being told, Luffy figured it out without being told anything about CoC being wieldable.
Zoro knowing about it or not is actually irrelevant, fact is he has been using it.
Zoro used CoC against people without it, and almost died in the process - he barely won against King and barely defeated Lucci (someone who doesn't have it either).
Luffy has been fighting people with CoC, developed it whilst fighting CoC users (Emperors/Admirals) and defeated them.
Zoro is using it against someone without it - in a sense, in comparison, he's fighting fodder compared to the opponents Luffy is using it against.
We saw what Imu did to Zoro, CoC would not have changed that. Luffy actually held his own. So, there's literally no comparison to be made here. Zoro's simply inferior to Luffy no matter how you look at it. He was using it against Lucci and barely won/Luffy pretty much defeated an Admiral. There's a big difference in the level of skill in usage and power between the 2.