It is unlikely anybody would store spatial data in such an inefficient format, but of course once you have obtained the data in some format you can easily convert it to WKT. Perhaps, then, you will be satisfied with the answers at http://gis.stackexchange.com/questions/5114/where-can-i-obtain-an-up-to-date-list-of-us-zip-codes-with-latitude-and-longitud, which show where to find Zip code spatial data.
– whuberJun 12 '13 at 12:33