Well, for one, I did not say skill plays no role. I only said it doesn't play a role in determining how strong someone's CoC is. Skill always matters but it doesn't dictate how strong your CoC is because your CoC is directly proportional to the user's strength. That's all I said. As for why Zoro in particular triumphs Yamato, that's because his CoA was already strong enough to fight off her CoC, so adding CoC on top would only make things easy for Zoro.