If it is still possible to use the 00000 zip code when no tuner is configured, it is since Plex Web 4.57.4, impossible to use this trick to add an additional Plex EPG when you already use an XMLTV file. You get the following error message:
Unsupported location
This location isn’t covered by Plex DVR guide data. Because you already set up a tuner using Plex DVR guide data, we are unable to offer the option to use a XMLTV guide. Please select a different location.
It is now impossible to have a configuration where you mix XMLTV and plex EPG. And that’s a pity because the Plex EPG is nice but doesn’t cover all my channels and it’s impossible to get them without an XHTML complement. 
