The + button doesn't work on Firefox (143.0.1; Linux; flatpak; x86-64). The - button works and so do other ways of zooming in (scrolling, double click).
Even when I worked for Medicare I couldn't get the damned post office to give us accurate zip code data! It's terrible geodata but also almost everybody remembers it and most zip codes map to one county, so it was the best UI we found for getting a general area for where a person lived.
yeah! There are like 12 three-county zip codes, some are really fun, like places where a boat delivers the mail and goes to multiple states along the lake. And some zips don't refer to geographical areas at all, and others are military bases.
It was still the best UI option despite that - if you entered a ZIP that corresponded to multiple states/counties we'd pop up a second box that asked you which you lived in, but for 99% of people it was all we needed