In total there are forty ZDC chips scattered around the city, 10 in each zone. The ZDC chips are not available until the side mission is given to you by Cora. These chips are located by blue side mission waypoints making this virtually impossible to miss unless you choose not to do the sidequest. When you arrive at a waypoint you will find two kings. Kill the kings, and each will drop a chip. Once you have all forty the achievement will unlock. The best time to collect these is while you are waiting for Nelson, alongside the other collectibles.