Personally, I don't really use ZDL to launch multiple mods, but I'm going to assume that ZDL doesn't take .zip files, so the best thing to do is to rename the file extension to something like ".pk3" or ".wad".
Then again, don't really take my word for it as I don't use ZDL.
Sorry for the late reply!
WooD_Lusting
Your local joined
The trees are screaming for me! Out of my way, mortals!