No fair! They're using brains against us! We removed our brains to make room for guns and explosives!
They're an alternate to the square trackers for resources, zed track events, etc (the chits with gray corners) so that they are easier to differentiate from the regular chits. You can use either ones you prefer.
Also note that the tactics level marker (the strip along the bottom) is designed to be cut out as one strip and folded in half so one side has 2 above the 4 troop type images and the other side has Z above the 4 troop type images.