One thing I will say is that it would be much harder to notice the consequences of your haki getting bested when you primarily fight with top of the line katana
These same high grade katana Zoro utilized pre time skip, before CoA, would rarely be in danger of getting damaged due simply to the high quality of the blade. And so now with only even the slightest of reinforcements(added with CoA) it’s safe to assume they’d be similarly safe from something like getting your blade bit into by Hody
Would Zoro’s CoA protect his flesh from a Yonko commander’s sword strike if he had no weapons to defend? I’m unsure; although it seems like Zoro is more adept at applying haki to his weapons(controlling the flow of haki) while Luffy has more feats reinforcing his own person, as well as feats where he makes up for the difference in hardness with superior force/striking potency
Either way, whether you pick pre Wano Luffy or current Zoro; based on Apoo blocking his sword with a tonfa; it’s clear that Zoro’s own top tier applied striking force may make his haki look greater than it is when it’s just Zoro’s sword techniques being that strong and not necessarily just his haki
Imho it’s definitely overlooked how applied striking force is just as important as your haki’s hardness. If that wasn’t the case than Marigold dookies on Amazon lily Luffy, and Luffy receives way more obvious physical strength buffs rather than just haki flow control.