Rockman ZX for the Nintendo DS ships on July 6 in Japan, and will ship in the US in September as Mega Man ZX. Game Watch Japan revealed that if the Game Boy Advance slot contains either Mega Man Zero 3 or Mega Man Zero 4, special features are unlocked. Apparently, playing ZX with one of these two cartridges allows gamers to fight the bosses from the Zero series, adding another dimension to the game for die hard Mega Man fans. While this functionality hasn’t actually been confirmed for the US version of the game, this feature would seem to be a lock.