It's always active. It's literally the ability of the blade, which Zoro has mastered. It doesn't have an on or off button
The fact is there was no such thing that you are talking about when Zoro or Oden cut Kaidou, as simple as that.
The attack was laced with CoC? Now you show me that. Kaido has also said Luffy has CoC just from feeling it. Doesn't mean his attack was laced with it. It's Ryuo.
It was though... that's the entire narrative behind RT that CoA was shallow & CoC cuts/hits deep enough to wound Kaidou - shown with both Luffy & Scabbards.
The entire purpose of Kaidou mocking the Scabbards attempt and telling them they are powerless to even reopen the scar and praising Zoro's CoC after taking a full on attack from him, which coincidentally leaves a scar, is literally to highlight that.
how yout hink he got acoc ?
He let enma take what it want and Enma went so deep in his haki he reached his coc .
Same happened with kaido and ashura .
Zoro said it himself he put everything he had in this attack so he let enma acces his coc without noticing it .
This is legit how he unlocked it vs king .
Let enma do his thing ! Survive long enought to win but if to much of your haki get drained you will die . (Legit what he said himself)
The Kaidou sequence happened as you said, when he gave everything he had and Enma accidentally pulled CoC out.
Heavily disagree about the King sequence though.
He was basically feeding CoA to Enma to satiate it and further decided to give it CoC.
Made a thread about it a long time ago with panels, explanations and stuff, we can discuss there if you want:
https://worstgen.alwaysdata.net/for...-requirements-and-what-is-king-of-hell.21792/