For adding new books see -
Preferences>Add books->Adding actions->Auto-merge added books if they already exist->Create new record for each duplicate format
For existing library try the following. Test on a few books first
uncheck this setting ===>>>
Preferences>Add books->Adding actions->When using the "Copy to library" action check for duplicates with the same title, author and language
- Create a new library, we'll call it TempLib,
- Search for books in existing library (MyLib) that have CBR and CBZ
- Copy those books to the TempLib library using the Copy to library tool.
- Remove all CBRs from the TempLib library
- Remove all CBZs from the MyLib library
- Copy all books from TempLib library to the MyLib library
- Remove the TempLib library
Curious, why don't you want both formats in the same 'book'? Indeed why even retain both formats?
BR