KOH is not Adv. CoC, it's not even Adv. CoA, and it's not even an Upgrade to his Techniques,
We've already seen what King of Hell does when Zoro tried to use Enma first time, He simply mastered that,
He learned to cooperate with his Swords rather than restrict them,
King of Hell is written before "Sword-Style", not after & before Technique,
It's a Variation of his Sword-Style, not Next Level,
When Zoro performs any Technique, He decides how much Power & Speed & Haki ... etc to put into it,
It's like opening a valve, King of Hell is just Zoro leaving that Haki valve open, that doesn't count as an Upgrade, just more serious & effective way of Fighting, however letting his Haki flow like that first time, ended up revealing his dormant Haoshoku Haki,
When Enel uses 200M Volt Amaru Form, it doesn't mean He upgraded his Lightning, it's just that before that Form, He must choose his Output & it's up to 200M, so Amaru Form is just Enel readying his entire Body to fight at full power at any given moment if needed, same for Kaidou's Flame Form, or Pica's Golem Form ... etc It's not like Base Pica can't attack you with only a Golem-Sized Punch, or that Golem Pica can't attack you with Human-Sized Punch (Which He did), those Forms is just them readying 100% Output for quick use,
Base Enel attacking you with 200M El Thor or Amaru Enel throwing that Attack, is exactly same, there is No Upgrade, just more Battle Ready.
Same thing for Zoro, King of Hell Mode is just Zoro being more Battle Ready & keeping his Full Scaling unlocked.
Zoro's Attack that removed King's Mask didn't have Adv. CoC, his Rengoku Oni Giri & Bird Dance didn't,
His Finisher against Lucci didn't, his Attack against Nusjuro didn't, his Attacks against Seraphim didn't,
His Attack against Imu didn't, They are same Techniques He learned to perform with Mihawk, nothing more.
Only questionable Attacks where Zoro might or might have not unconsciously used Adv. CoC were his Final Attack against King & Asura Attack against Kaidou, all others are just CoA.