Board Thread:Questions and Answers/@comment-13442349-20130726072748/@comment-11051098-20130802205519

Good point BassGod, I never thought about that.

He lost his heard when Ulquiorra killed him with Cero Oscuras, and regained his heard in the shape of a new Hollow mask when Hollow Zangetsu took control over his body. Then, when the new mask shattered after Ulquiorra cut off his horn and his Cero imploded, he regained his heart again.

It makes sense.