Zipper is the second fastest land unit in the game - only jeffy is bit faster. It is equipped with a rapid-fire machine gun of a very short range. Useful for raiding unprotected structures, slow artillery etc. Thanks to its speed, it is also effective to build it as the last addition to your pushing force. When the heavy duty frontline breaks, Zippers may sneak in and deal the final unstoppable blow.
Super hard to D-gun, hence a good way to destroy unprotected commanders.