people understimate the magnitude of zoro's feats in chapter 1009-1010.
he was weakened beyond believe, all bones in his body broken, and yet he managed to pull out asura, blast CoC and scar the WSC.
lets put things into perspective:
- whitbeard was WSM and during the summit war he couldn't use CoC and CoO, and his CoA was trash, all because his body was weakened due to sickness.
-we all know that sea stone severely weakens devil fruit users, it drains their energy at a massive rate that luffy & kid went from being morbidly obese back to their normal shapes in a matter of seconds.
- in yamato's vivre card it was mentioned that her handcuffs were made of sea stone, yet she could use both her devil fruit and haki quite comfortably, but in luffy's case when he was imprisoned in udon his conditions were much severe, even though his sea stone cuffs were designed to have a mild effect, he couldn't use both his devil fruit and his haki, he was breathing hard, and he went down in one hit by babanuki.
- gear 4 uses to much haki, which puts a lot of stress on the body, after luffy runs out of energy, he suffers the same punishment (although temporarily) as being handcuffed by seas tone, and can't use haki for 10 minutes.
physical condition has a great impact on haki usage/potency.
zoro wasn't just weakened, he was
utterly destroyed with no means of recovery, which means that he shouldn't even be capable of standing let alone use haki, yet the grandmaster persevered through all that, played his role in taking down big mom to the fullest, and last but not least he outclashed kaido and scared him for eternity.
zoro has the greatest feats in the series.