What’s the difference between city and zip code targeting?
Targeting by city means just that: Your ads will be targeted toward users within the boundaries of that particular city. Since most medium- to large-size cities have more than one zip code, you now have the capability to specifically target only a portion of a particular city through zip code targeting. Note: Targeting by zip code can dramatically reduce the number of search users who will see your ad. Therefore, if you find that your targeting strategy includes almost all zip codes in a certain city, you may be better off targeting by city to expose your ads to more users.