He probably didn't, because Yhwach didn't use it. There's no reason why Zanka no Tachi wouldn't be nullified by The Almighty when we see a lesser version of it [Bankai medallion] stealing its power. Course, that's assuming the potency of the eyes remained the same 1000 years ago.
Chances are that something happened that made him unable to use it in the invasion. Maybe it had something to do with Haschwalth, or maybe he sealed it for some reason. I'm sure that Yamamoto would have noticed the change in the eyes when he fought Royd. Plus, Bachgetsu's eyes didn't resemble the Almighty so at some point 1000 years ago, he must have not had them.