Power Mochi is just an extended version of block mochi. Zangiri Mochi is much stronger than Power Mochi. Katakuri didn't use power mochi against snakeman because it was less effective than cqc. What are you trying to say? That Katakuri was holding back? Lol.
And it is clear that Zoro has an advanced form of CoA. That was evident from how important Mihawk deemed CoA to be. You can literally see black energy flowing out of Zoro's swords when he imbued them with Haki.
+ Zoro is just about to even improve his Haki. As you can see, it is not just the sword that is powerful. You have to master it or else it will suck you dry. Once Zoro masters that sword, it will mean he mastered his CoA even further. Plus, just as Luffy grew
during his fight with Katakuri massively (gaining FS), Zoro might as well grow
during the fight with King. Let's see how strong King's Haki is.
I don't get it. We don't even have feats of King and you already say he is weaker than Katakuri. Lol.