Zeke actually knew who Kessler was, and was working with him. Since Kessler was around for decades before they were born, he would obviously know who Zeke was before birth, making it easy for him to track him down. Before the blast, Kessler contacted Zeke, clued him in on the whole thing. It took him the usual time-traveler friend schtick for him to accept that he was Cole from the future. Or perhaps...Zeke is now a member of the First Sons long before the blast...He wears stars on his clothes.... Either way, Zeke worked with Kessler, which was why Zeke tried to activate the Ray Sphere and left with Kessler, it was to completely destroy Cole's sense of trust, and to cut an emotional bond with Cole, preparing him to harden his heart to be able to go into battle against the Beast unhindered.