Came across this forum today suffering the same problem. Mine is a bit more extensive, but same roots.
I too downloaded three Dragon Age: Origins mods from this site in .zip format. It has nothing to do with the browser in this case, I checked that.
I noticed that MegaToxic's "Wings of Velvet" mod was shared as a .dazip file. So I think his isssue was with managing the DAUpdater/Mod Manager. My three mods however were shared in .zip format to begin with. In other words my mod never actually contained a .dazip file from the start.
MegaToxic's "Wings of Velvet" mod= https://www.nexusmod...es&file_id=3312
My mod "Grey Wardens of Ferelden"= https://www.nexusmod...s&file_id=17152
Following some guides elsewhere I extracted the mod file using 7-zip to the override folder (I didn't actually have that folder and had to create it) this too failed however.
Any help or attention is appreciated.