What you need is to GeoCode your address, then get ZIP from GeoCode.
you can do it via Javascript and Google Map API, not hard at all, I also know it can be eaiser done in XCode, there must be very common in other language, try google search GeoCode
you can do it via Javascript and Google Map API, not hard at all, I also know it can be eaiser done in XCode, there must be very common in other language, try google search GeoCode