In these 10 video tutorials you will understand how you can use Zsphere modelor to create models which can be manipulated, transformed, skinned and converted into 3d poly mesh and can be added as subtools. These tutorials created by the Pixologic (makers of ZBrush) for the 3D community, so everyone can easily go at advanced level in ZBrush and extract the full potential of the ZBrush. As always you can also download the files in flv format for later viewing.
LINK:
http://www.cgarena.com/freestuff/tutorials/zbrush/pixozbrush/zsphere_subtools.html