"breathing heavy" as you say is not measurable damage.
luffy hit kaido way more times than zoro did and with way more potent attacks(ADV COC coating).
like I said, the most notable thing zolo did was put a scar on him and he didn't even knock him down like Oden did.
go back and read. before they even launch the attack luffy uses futuresight. after zoro holds the attack off for a second law transports zoro, kidd and killer NEXT TO HIM. thats why killer asks "wheres strawhat" and we see hes already attacking kaido while they are recovering.
like i said luffy was the only one to dodge the attack