You should def be getting a .zip. If you are not that means your browser/OS is automatically unzipping.
I've seen that ARIS uploads but doesn't dismiss the upload with these files. We need to fix that before going to the public editor. If you dismiss and refresh, your targets should show up.
That said, I just downloaded something via safari on OS X, which auto unzipped. I re-zipped and I never could get it to work. I ended up clearing the safari downloads and zip files I made, then downloaded from vuforia in chrome. Everything worked great.