Though ultimately it was far too granular (for example the Bay Area would be so many different zip codes). Instead we went with Nielsen's DMA (Designated Market Area) mappings within the US to abstract aggregated data a bit better. And of course this DMA dataset also had a different original use case. It was used for TV / media market surveys so it has some weird vestiges. Some regions are grouped very far and wide (you'll notice there's a bit of Denver within Nevada and its just a remnant of how it used to be categorized), but it still provides a bit of a broader level grouping than something acute like zip code.
I do like this map from the article though and the granularity you can get with zip code when zooming: https://clausa.app.carto.com/map/29fd0873-64cb-42a6-a90d-c83...
We've also been considering using Combined Statistical Areas using population instead. This is something that is under way, and in the interim we've considered charting styles that don't necessarily need borders (for example this bubble map: https://www.levels.fyi/bubble-plot/europe/). The benefit with DMAs is that it offers full border coverage of the entire US whereas some hubs can still be missing from CSAs if relying on a population threshold. But the plan is to create some of our own regional definitions and borders using our own submissions combined with population. Will be an interesting project.
GeoJSON data for the map borders: https://github.com/PublicaMundi/MappingAPI/blob/master/data/...
Nielsen DMA regions: https://blocks.roadtolarissa.com/simzou/6459889