That archive has a folder named
. in it, which doesn't make sense and is a mistake on the part of the tool which made the archive.
Opus will not open an archive with that in it, because
.. filenames are not legal in Windows and archives that use them are potentially malicious.
Archives with those names could be designed to trick tools into extracting files to locations outside the destination folder (e.g. to replace things in the Windows or Program Files folder), so Opus simply won't open them as a precaution.
(The Archives plugin handles things slightly differently, and will rename the folders from
_ instead of refusing to open them. The above explanation only applies to the internal Zip code.)