I see that Algalon is as stupid as always Lol Who cares if Luffy is 100 tiers above Zoro? Not me at least, so i hope that makes you better sleep at night
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Concerning the haki matter, i'd say that sure Luffy displays it practically on every and each panel he gets focused on, but does it really matter? A character isn't forced to use haki in every and each panel he gets focus on to know he has it, a character isn't forced to use it in every and each panel he gets focus on to prove his superiority in haki to someone who does. We have admiral Fujitora who rarely used haki yet(presumably). It depends on the character and capability. The thing is Zoro accomplish comparable feats to Luffy presumably without use of haki(presumably because invisible armament can happen), so Luffy enforcing all his hits to
only replicate Zoro's feats is a testament in Zoro's skills if anything
On a side note though, Zoro used
1- COA barrier against Hyouzou
2- COO to detect Cariboo in the castle(while sleeping)
3- COO to sense Vergo's aura in the lab
4- COA to cut Monet's cheek
For the last example also pay in mind he incorporated it in the thin air, something we've not seen someone else doing(not saying they can't though). Coincidently though, Oda always seemed to make his armament usage happen off-panel or unexplained as if he was trying to preserve it for a later event. The fact remain however that we already know he has it. So you can't be bothered if he uses it or not in every and each panel he gets focus on when he isn't forced to. He could have used it against Monet for example, but the truth is he couldn't be bothered by her, hence he cut her vertically without applying haki to show her she would have died had he been serious. Zoro trains to be able to cut anything, which is probably the reason why Oda decided to make him more specialized in COA.