Um are you forgetting that Kaido was literally gonna lose to Oden? And that he required that distraction on Oden to survive?
yes, Oden did in fact do MUCH MORE against Kaido… He was gonna win in two hits against younger Kaido and Zoro was NOT gonna win in two hits against older Kaido
Zoro (and by extension Oda) said Oden is stronger than him. And that’s simply the truth of the matter… and since Zoro is by his own admission weaker than Oden, Zoro could not have scarred Kaido with just COA yet Oden required CoC to do it