Quick answer
In which chapter does Zoro use Conqueror's Haki?
Verified through chapter 1010Updated
What the manga shows
3 factsKaido recognizes that the distant silhouette possesses Conqueror's Haki during the fight.
Kaido confirms the fighter can coat attacks with Conqueror's Haki.
Zoro is the silhouette Kaido addresses after unleashing an attack on the dragon form.
Change log
1 chapter- Chapter 1010Added 3 facts; updated the answer