The latitude and longitude coordinates are to only be used for mapping purposes. They are available in the kml, which can be used for google earth. They are not available to extract or download otherwise.
According to google terms:
No mass downloading. You will not use the Service in a manner that gives you or a third party access to mass downloads or bulk feeds of any Content. For example, you are not permitted to offer a batch geocoding service that uses Content contained in the Maps API(s)
USA Zip codes with latitude and longitude can be found here:
There are many other places to find USA zip code data as well.