Courier companies have divided all serviceable pin codes into multiple shipping zones. Each shipping zone has multiple sets of pin codes and a definite definition. Your shipping metrics like Freight (Forward & RTO) Charges and Delivery Time depends on the shipping zone in which your selected pin codes falls.
How courier companies define shipping zones in Shiprocket:
Zone A (Within City) - If Pickup and Delivery pin codes are in the same city.
Zone B (Within State/region) - If Pickup and Delivery pin codes are in the same state/region.
Zone C (Metro to Metro) - If both Pickup and Delivery pin codes are in metro cities
Zone D (Rest of India) - If any or both pickup and delivery pin codes are in India. This excludes any pin code of North East region and J&K region.
Zone E - If one or both cities are in the North East region or in J&K.