Like all other ZBrush functions, the ZModeler brush is affected by any masks on your model. Additionally, you can temporarily change to the current Mask brush by using the standard hotkey. (Ctrl)
The default masking behavior will prevent Actions from affecting the masked points, edges and/or polygons.
A Masking Action is available in the ZModeler brush to produce quick masks based on Targeted points, edges and/or polygons. Once masked using these Actions, the model can be manipulated with TransPose for accurate transformation.
There is also a TransPose Action that masks the entire model except where Targeted, then automatically switches to TransPose mode.
When working with a mask, keep in mind that its representation is based on the points of the topology (just like Colorize PolyPainting). With very low resolution models it can be difficult to visualize the mask.
All the masking functions found in the Tool>Masking sub-palette work with ZModeler.