When could it happen ? Zoro will be too busy fighting Kaido to be able to fight King later
I know you aren't fan of Zoro vs King now but it is best to stay open minded as there can be a curveball anytime before Zoro helps vs Kaido
Jack was speculated not to fight the dukes when the scabbards went to the roof with Kaido, guess what happened? Jack followed them and the dukes got to fight him.
King can follow Zoro to the roof at any time and they battle before Zoro helps vs Kaido.