Trouble setting up a search for a single field
You can do this with Views.


Install Views.
Go to Structure>Views then + Add new view.
Set Show [content] of type [Your Content type here] (also tick Create a page) then Continue &amp; edit button.
Under FORMAT select Show: Fields. Then under FIELDS click Add button and add the fields you want to show in the result. Then click Add button next to FILTER CRITERIA and add your zip-code field. On the settings screen of that field tick "Expose this filter to visitors, to allow them to change it".