I was reading an update on a SHOC mod page on Moddb which was talking about this and explaining what needs to be done to the files to allow it to work with 1,0004 mods. It was not a lot that needed doing but you'd need to go and hunt out the mod and it's update as I cannot remember which or when all I can remember is that it was within the last 4 to 5 weeks. Sorry but I don't remember which mod it was an update for.
Everything you want to know about Degtarev's zone is in the: COP Survival guidehttp://cop.zsg.dk/
1. Re-install the game, and backup installation folder (at least .db files and "bin" subfolder) prior to applying any patch.
2. Apply Patches 1.0004, 1.0005, and 1.0006 one after the other, and always backup installation folder (as above) after patching.
3. Now you got a backup copy for every version. Just restore the version you need by replacing the currently installed files.
Alternatively you could make different installation folders for the different patches and run just the one you need (you might also need to copy the mods in the correct installation folder, of course).
Something considered impossible is only something that hasn't been done yet.