There once was a Zam whose soul was split infinite times, and each time Chaldea summoned a servant, it was actually a Zam cosplaying with some little attached spirit origin borrowed from a big Zam cosplaying as Alaya and another big Zam cosplaying as Gaia. All of the servants, enemies or friends, are all split Zams. Fujimaru doesn't know that he's surrounded by Zams.