We added an API to get results on a multiple zip codes API request:
http://www.zipcodeapi.com/API#multiZipToLoc
Use this API to find out the city, state, latitude, longitude, and time zone information for multiple zip codes. The JSON and XML responses contain alternative acceptable city names for a location. Send a GET request to:
http://www.zipcodeapi.com/rest/<api_key>/multi-info.<format>/<zip_code>/<units>.
Each zip code provided counts as a separate request. For example, if you send 5 zip codes, you will be charged for 5 requests. Any zip code not found will not be included in the response.