ZCKA or Zoro Cuts Kaido Again is phrase popularly coined by twitter and discord user, @MistaZod.
Unlike ZKK(Zoro Killing Kaido), ZCKA does not mean Zoro kills Kaido but rather he cuts Kaido again except this time equaling or surpassing Oden's nearly mortal strike on Kaido. ZCKA devotees believe that Kaido will dub Zoro as the samurai as monstrous as Oden at the end of the arc.
ZKK? No, I'm a ZCKA believer.
ZKK is possible but ZCKA is guaranteed to happen.
Stands for Zoro Can't Kill Anyone, the best theory ever in One Piece.
"ZCKA is happening everyone ! It always has been!"