Well, at least the problem isn't the mod itself.
Have you checked on
Larian's Discord? There are other modders there, as well as possibly people from Larian who can offer modding support.
How large is the mod? If you can zip and email it to supportdos2@larian.com (or a Dropbox or Google drive link, etc), I can try it here, and if I get the same error, see if someone that works with the editor has any suggestions.
Depending on the data,
7-Zip's .7z format may have better compression that zip.
