Zhou was laughing wildly throughout it, and when her reiatsu finally started to take an upswing and she was capable of standing her ground, he didn't fall back.  He simply kept attacking, knowing that he was going to get hurt one way or the other.  He had to force her into doing what needed to be done.  Force her into tapping all that hidden strength and unleashing it in a monstrous assault upon him.  She -had- to get better, as did he.