Way back in Sabaody when Luffy used COC for first time,Zoro had a similar moment.In fishman island,when Luffy used coc to ko 50k fishmen Zoro commented:"anything less and I would have to take over as captain".Punk Hazard:intimidated Monet into defeat basically.Zoro was hinted many times as a COC user,Oda was just saving it for an epic moment like this and he delivered.
He can tango for sure but I doubt he can win on the long run until he shows more
I stand on my opinion: that King would only win after an extreme diff fight. I can see why someone would argue that King high diffs, just Iike I can see someone argue that Killer extreme diffs.
Everything on the lines of "King/Killer low/mid diffs" is BS and not worth debating.
I'm sure Zoro was talking about both Luffy and Kuina at the end. Earlier in the chapter, Zoro remembered his oath to Kuina that he would become the World's Strongest Swordsman. And he has only ever referred to Kuina as his "dear friend."