z axis
depth axis; moving front / back

z channel
A channel/image that provides z-depth information to help artists reproduce an illusion of depth.

z space
Pertaining to the depth (front to back) of an object and how far it is from the camera.

ZBrush / Z Brush
a common software used to sculpt more intricate details on a 3D object. 

zoom / Zoom
A camera or frame adjustment that makes an object on screen appear closer (zoom in) or farther away (zoom out) from the camera without actually moving the camera in space.