Hehe
Example using the map border texture file;
When you create a zip-file, the folder structure inside, should be:
"res_mods\version\content\location\misc\gameplay\textures" and in the textures folder would be the file.
Check the DLC Cache folder, if you have installed through the modpack, you might already have a perfect visual example in that.
Since those zip files are packed like you should be packing your custom mod zip.