Is there really no ZIP code that is non-contiguous? I think it might depend on the visualization provided by services, but it looks like on Google Maps, searching for "92014" seems to generate borders around two areas that look like there is no contact between them.

Zip codes are trees, each digit narrows down the area. The final area can be non-contiguous, but 92014 is entirely contained within 9201, that's within 920, etc. up to 9, which is the US west coast area.