Just a quick lesson in terminology:  A zone is an area controlled by one thermostat.  Your house might have a single thermostat or zone for the whole house, or some have a separate thermostat / zone for each floor of the house, and some like to have complete control and have a separate thermostat / zone for every room of the house.   The choice is yours. However, when laying radiant floor tubing (Pex) you will most often have multiple loops of tube in a single zone.   You should never have a loop more than 300’ long and each loop in a single zone should be the same length.  A manifold connects all the loops together and makes one zone.

The picture below shows many loops, but just one manifold; so, this is one zone and will be controlled by one thermostat and one pump.