could still be a folder in a folder type issue. They don't allow to many subfolders (there exists a zip file out there that breaks things by having massive numbers of sub folders) they limit it to 1-2 deep in order to avoid exploits.
I would try highlighting the 4 images and adding directly to a zip file (no folders inside the zip)
So basically all I did was put four pictures into the file. Then I compressed the file and tried to upload it but Icame with this error. So I was wondering if misnamed the pictures in a way or if I was suppose to compress it in a different way.
Oh i was able to figure it out, when I opened the file on my mac it was just one file, but after exploring it on my phone i noticed there was an extra file that wasnt there before which showed up after i imported it out.