The main purpose of this legislation is to require the United States Postal Service to create a single, unique ZIP Code specifically for Eastvale, California. This is intended to improve mail delivery and address identification for residents and businesses in the area. The key provision of this legislation mandates that the Postal Service must establish this unique ZIP Code within 180 days of the law being enacted. This means that once the law is passed, the Postal Service has a set timeframe to implement the change.