Eh, I'm not going to scale on length. King took 4 KOH attacks to go down, three named and the finisher was a super technique ("King of Hell Three Dragons").
But besides that, the attitude/demeanour is different.
Zoro recognises and respects King's strength, but tells Lucci that with only this much power he won't let him fight Luffy:
And this is basically the same thing he said to Pica:
There's a difference in how Zoro is treating the two as opponents.