I don't know, he must have modded MyHouse.wad in order to make it work with Peppino or he extracted Peppino into its own mini-mod. Either way I don't know.
Try to launch the game using the Windows command executable. if it doesn't find the file Zandronum will ask you to direct it to the file containing the Doom2 wad and it should launch afterwards. That operation is only necessary to do once.
When loading BYOC, try to drag and drop only the BYOC pk3 onto the Zandronum launcher. Zandronum should automatically detect the Doom2 wad if it's in the same folder as it. There shouldn't be a need to extract the files contained in the wad or, in this case, the pk3, this would only break the reading process. There is a chance that your download was corrupted at some point. I've downloaded the two different files on my side and these work perfectly fine. That is the only explanations that came to my mind, I hope you will be able to play our mod. Maybe try to put the solo pk3 into the all in one file. Maybe that will fix the problem since the pk3 seemed to be broken in the latter on your end.
with the all in one, did you put the Doom2 Wad where it asks you to put it? And then run the BYOC Singleplayer.bat? Because that may be caused by that.
For that we recommend that you use Doomseeker. It's a plugin that enables players to easily search and look for servers. You should be able to easily find tutorials on how to install and use it. It works in tandem with free server hosting websites: The Sentinel's Playground which is located in the USA or Euroboros for servers hosted in Europe.
