What you just said made absolutely no sense.
ACoC it just the term us readers created. It just means CoC coating. You don't unlock that you just learn to flow it and coat your attacks or weapons with it. The black lightning around his swords are CoC. Oda let us know that black lightning was CoC by having the fodder pass out due to the black lightning.
Enma it's not doing anything since Zoro has fully mastered enma. He's the one in full control and the one manipulating his haki.
He asked how he should stabilize his haki.
Enma doesn't have any effect on Zoro's CoC or his other swords. The following scene shows all three swords contain ACoC.
The following scene shows us what happens when Zoro loses control of enma and it releases his haki.
There is no ACoC.
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The manga never told us that that technique calls him permanent damage. The manga told us Zoro asura attack caused Kaido permanent damage.
A needle could cause Kaido permanent damage if Zoro attack with it with his power. Whether Kaido receives permanent damage or not is based on the strength of the attack he is hit with.