Leahf's last mission with the Platinum Lantern Corps was to assault the Guiding Light and prevent two rogue Users, The Architect and LordMalygos, from reaching Vizima. During the conflict he led a squad which also consisted of Barsu and the Expendable Reptilian Lantern. When he arrived at the scene, he asked them to come quietly, but was fired at by TA in his ship. After the ship was damaged, Quolas and his squad arrived to help. Zimmer eventually convinced the two Users to surrender, and escorted them back to their HQ to meet MY.
After the mission, he chose to retire from the Corps. Per regulation, he handed in his power ring and was dropped off at a nearby space station by Quolas. He went over to a bounty board to see if he could make a living in the mercenary business, and from there he met Jaxidak Yik. Jaxidak introduced himself, and told Zimmer that he could use someone like him to help him track down Zax, a Terugan outlaw who had stolen something of his.