“In these 3 video tutorials you will understand how to create a new geometry from the existing geometry using the mesh extraction in ZBrush. 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.”
http://www.cgarena.com/freestuff/tutorials/zbrush/pixozbrush/meshextract.html