Complex sentence: The postcodes start with 0 in Northland and progress southward, ending with codes starting with 9 in Otago and Southland, making the new system similar to the Zip Code system in the United States.
Split into simpler sentences: The postcodes start with 0 in Northland and progress southward, ending with codes starting with 9 in Otago and Southland. Making the new system similar to the Zip Code system in the United States.