I am writing a phone app that allows users to access clients via zip code proximity. How do I set this up?

If you start with this post here it will have very useful information.

https://community.quickbase.com/quick...

There is an enhancement which can be added to ensure that the users don�t trip over each other. But maybe get this far first

There are free downloads available which cross reference zips to lat longs.

Zip code download for grocoding

https://gist.github.com/erichurst/788...