I'm not convinced that Coronado didn't split up the expedition at certain points, perhaps while investigating possible routes. Seems like most researchers are wedded to the idea that it stayed in one piece and followed only one route.
An army like that traveled on it's stomach, and there is very little to eat out there that would have been obvious to white Europeans. Smaller groups on different routes, with the idea of meeting up later, would make it much easier to keep the men fed.