To make the informed choice, you need to know the lingo. Learn it here.
A geographical area. A geological zone, however, means an interval of strata of the geologic column that has distinguishing characteristics from surrounding strata.
A method of developing zoned rates. This method involves first segregating costs by zone as if each zone were a separate entity, then developing the unit costs of gas flowing through each zone. The customers in downstream zones pay the costs associated with their gas flowing through the upstream zones.