This was not obvious, being a programmer I assume that the .img needs to be extracted. However the rpi imager will happily write the .zip file to the SD card (not sure if it extracts it prior).
If this is the case that it needs to be unzipped, a mention on the wiki would be helpful, as the wording seems to indicate that the file can be used as-is.
Admittedly, I may be wrong about this! It just seems weird that a zip file can be written straight to sd card, unless the software transparently unzips the file first before writing. So some clarification would be good either way.