The archive has an empty folder named . at the top level, which is illegal in Windows (. is a special folder name which means "the current directory"), and path names like that in archives have been used by some exploits to trick unpacking tools into extracting files outside of the target folder (e.g. into folders below Program Files instead).
Opus detects and rejects such archives for security reasons.
I recommend telling Synology to fix the tool that created the archive, since a folder named . should never exist in a zip archive, at least not one intended for extraction on Windows like this one.