We don't what BB has up his sleeve though. Also plot won't allow BB lose where such a fight take place
Basically Zoros 2 sword base Strength seems to he above Sera Hawks and Blackbeard needs Haki to block. Zoro has his own Haki..I mean 2 advanced Hakis as well..idk..he's lose his arm if he tries blocking Zoros CoC attack like that
the question is no longer "Where does Zoro fit on the OP power scale" its "How much do we need to change the power scale to fit Zoro"