Marco is canonically weaker than King and got defeated by him
Marco was "defeated" (he gave up as the stars were about to take on the Calamities, he still can move, use his flames, carry others...) by King and Queen together since he was exhausted because of how hard it's to deal with the two of them at the same time. This is explicitly stated, so, if anything, King couldn't K.O. an exhausted Marco.
Yet Big Mom had serious duel with Marco and ran away saying she doesn't have enough souls to defeat Marco.
That 100% confirms he cant defeat Marco quick.
Nobody can defeat Marco quickly, that's his gimmick. He has a mythical zoan based on regeneration.
Zoro post AdvCoC QUICK low diffed King as he has to before virus kicks in.
Luffy's jet gatling neg-diffed Lucci? Since we're ignoring whole fights and the effect of fighting for a long time plus equalling basis performance to finishers...
Now Zoro body bags Big Mom by feats, portrayal and hype.
Big Mom's portrayal as an emperor of the sea, facing the two more prominent captains of the Supernova apart from Luffy, explicitly put on Kaido's same level and so on is enough portrayal on her side.