But if Zero is "black" as Botan has just informed Motoko's grandmother, the others being Hifumi's respective colors of offense (red), speed (blue), and defense (yellow), Zero should have a nearly perfect defense just as Izuru does. If she's fast enough and defensive enough, Zero might be able to avoid the full damage that comes from Izuru's counters.
It comes into question because all we've seen thus far is that Zero leans towards brutal offense bolstered by speed, and we don't know if she can equally switch to iron defense bolstered by that same speed to alleivate damage mid-counter.
Plus, going back a few chapters, if Motoko is the inscribed circle, Hifumi is the triangle, and Zero is the circumscribed circle, Zero knows everything (even Motoko's blocked past). Including the fact that Fujiko pointed out Izuru's weakness, anything at her back.
She has been working on it, but I question at this point whether or not Izuru can truly stop Zero with all those factors. So far it has just been conjecture and hope from Hifumi, Motoko and Kosukegawa.