User blog comment:Xilinoc/Ch. 605 - Don't Call My Name/@comment-5693502-20141113174043/@comment-493809-20141115060121

People have been looking at the Kenpachi thing the wrong way. Shunsui decided to have Kenpachi trained so that he could go kill a good number of Sternritter, like he did in Round 1. It was Yhwach who decided to send in his monster to keep Kenpachi from decimating his forces.

As for Aizen's Zanpakuto: don't forget that he messed up Yhwach's sense of time, and part of his speech to Ichigo involved speculation about fusing with one's Zanpakuto. Perhaps that's the true reason why he lost his - he's fused with the spirit and has its powers. Maybe now he has perfect illusion powers over anybody who sees him.