Could be part of koh could not be. When zoro was fighting king in the end when he better mastered enma it was sucking the life out of him. With him only stopping it after he beat king
He used king of hell onigiri, bird dance, and king of hell 3 sword serpent 103 mercies all while straining himself using enma
My only guess would be while overusing enma
- King of hell = full armament overuse (can include conquerors)
- Normal name = conquerors infusion
- 3 sword serpent = full armament and conquerors overuse