Sadly, your approach leads to several problems, the least of which is not even remotely achieving what you believe it to do: saving space.
By starting a program from inside an archive, you're forcing your OS to extract it's executable and any accessed file to temporary space. Which in turn requires you to keep (an unforseeable amount of) free space on your drive to accommodate the temporary files. It's also what gave you away to
TotesNotThea as it's readily apparent from the error screens you
provided.
That aside you're also saving way less space than you think you may. As most game assets are already heavily compressed (often using lossy but visually lossless compression) the main draw of packing them into an archive is ease of delivery. I went ahead and compiled a list of space requirements for v18 of the game:
Code:
zip 3.510.004.958
unzip 3.564.994.945
unren 3.564.761.286
delta 54.756.328
As you can see you're only saving short of 53 MiB. In other words: practically nothing.
Your approach is also the source of your
problem with unren.
I urge you to reconsider and follow the
instructions laid out by
lemonfreak but complement them as per the mod's authors instructions by using unren (for reasons I detailed
earlier). Good luck!