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Census data geometry boundaries (blocks) do not correspond 1:1 to ZIP Codes.
The Post Office does not use polygons to define ZIP Codes. Any map you see that shows ZIP Code polygons is only an approximation created by someone else.
The Census creates their own approximation, which they call a Zip Code Tabulation Area (ZCTA).
Here is a short Census video that talks (at a very high level) about the differences between ZIP Codes and ZCTAs: https://www.youtube.com/watch?v=dluu8NcTyrM
This Census page goes into a little more detail: https://www.census.gov/programs-surveys/geography/guidance/geo-areas/zctas.html
But this is the real gold mine – the best explanation I’ve ever seen about trying to use ZIP Codes with Census data: https://atcoordinates.info/2020/05/11/the-trouble-with-zip-codes-solutions-for-data-analysis-and-mapping/