Zip files can not be detached from PDF

Opening zip attachments depends on security settings of your PDF reader

Adobe Reader does not allow this type of attachment to be opened, so in PDF settings we have an option to overcome this issue.

You can choose to rename the zip extension to 7z (or any other, but with 7z you can open a file directly in 7-Zip or another program that supports that file type).

This setting can be found in the Attachments tab of your PDF settings:

Change zip extension to 7z