Goz zbrush - Isolate eyes & mouth to shape morphs properly

Hi, So far gozing to zbrush to make new morphs is great. However when I sculpt/move/etc, the eyes and mouth are affected in an unwanted way. For instance the eyes won't keep their round shape because of excessive operations, even if I try to do my best to preserve them. The ideal would be to split the mesh and isolate these parts, but the integrity of the mesh and vertex order would be corrupted and the morph won't be accepted. Any tips? Thank you in advance for helping.