As near as I can tell from the MUL at the moment, the first known variants of the Zeus BattleMech (5T and 5S) were introduced in 2787 and 2788, or about three and four years after Kerensky's Exodus, respectively. So when any Zeus at all, let alone the ZEU-6S whose introduction date is again set just over a century later, shows up on the Pentagon Powers RAT on p. 146 of Historical: Operation Klondike (specifically in position 8 of column C for assault 'Mechs, I can't help but wonder just what it's doing there...providing stealth evidence that time travel does after all exist in the BattleTech universe, perhaps? ;)