Welcome the Technical Support section. Help us in assisting you by providing us with a concise and descriptive elaboration of your issues. Be specific and if possible, provide us with a step-by-step instruction in replicating your problem.
STEPS TO REPLICATE:
1. create "Discussion"
2. Upload a file with zip extension
RESULT
with 3.x: I receive an error message: Uploaded file type is not supported.
with v4.2.2: file name is red and nothing uploaded
before you ask: I added the the zip and ZIP extension under the "Media" settings. I made a cross test and I removed this option. In this case the v3.x immediately informed me that the zip is not allowed
I installed iJoomla Installer and it is not installed the latest version - after a multiple upgrade now I am using the lates version and it seems the ZIP upload is working in the latest version.