districts.getZipsFromDistrict formerly existed to get all zips within a given congressional district
deprecated May 11th 2011, removed Nov 14 2011
This method was removed because of the difficulty in keeping zip codes and districts in sync as new zip codes are added and district boundaries change, we now use a purely polygon-based approach. districts.getDistrictsFromZip still exists and uses this approach to give an approximation, but if possible it is recommended that you switch to the latitude-longitude based methods like districts.getDistrictFromLatLong