The ZMap algorithm was proposed in the academic literature by Byoung K Choi in 2003 as a way of precalculating and storing a regular array of Cutter Location values in the computer memory. The result is a model of the height map of cutter positions from which in between values can be interpolated.
Due to accuracy issues, this was generalized into an Extended ZMap, or EZMap, by the placement of "floating" points in between the fixed ZMap points. The location of the EZMap points are found iteratively when the ZMap is created. EZMap points are only placed where sharp edges occur between the normal ZMap points; a completely flat source geometry will not require any EZMap points.
Read more about this topic: Cutter Location