Set folderEnum = DOpus.FSUtil.ReadDir(doubleClickData.item)
Set folderItem = folderEnum.Next
' If the first item in the archive is a directory:
If (DOpus.FSUtil.GetType(folderItem, "a") = "dir") Then
FWIW, that's not checking if folderEnum failed or if the folder is empty.
Check that CB7, CBR and CBZ are turned on in Preferences / Zip & Other Archives / Archive and VFS Plugins, based on the type you're trying to work with.
Hmm - I can't. Right clicking them also does not show commands to extract, like Opus forgot that these are archives. Tried several CBRs and CBZs. (not its not calibre, it just added itself to open with)