Also, Ground Zeroes is apparently 10 days after Peace Walker,
Actually, Miller only says he got word about Paz's survival 10 days ago. It sounds unlikely he'd get a message about that the same day.
I'm guessing since Chico was 12 in Peace Walker, and in the animal cage he looks around 17-19, that that we're at least looking at a several year gap.
They said in the trailer that 10 days ago they got info that Paz was just fished out of the ocean by a Belizean fisherman. That would mean its only been at most a month or so after Peace Walker. Chico still looks the same age (12-14).