Site content division based on users zip code.

I’m trying to create a website that contains a splash page looking for a users zip code.

Depending on what zip code is entered the site will display a different home page along with a few other pages.

There are only a few different content sections on the site that depend on the zip code while some pages display the same regardless of zip.

My questions is how do I got about doing this? Do I create two compliantly different sites or is there some why to display the content dynamically depending on the user zip code.

thanks