Make multiple fields *required for search

My client would like to require uses fill both of our search fields to search. I have two fields, a category ‘Select’ field, and a Zip Code field. Is there a core functionality to require both fields be filled before a search, or is there a quick way that I can tweak the fields in the plugin?

You can view the project here: http://miguelcontrerasfoundation.org/attorney-directory/

Core Plugin v. 1.6.19
Advanced Search Filters v. 1.4.8