When I want to change a .cbz (order, add, remove, or replace images) I do the following:
- copy it to the book's 'data' folder (if it doesn't exist I create it),
- prepend a timestamp to its name (sometimes),
- unzip the cbz,
- do whatever needs doing,
- zip the folder of images into a new .cbz,
- copy the new .cbz to the clipboard,
- use Add Books->Add files to selected book records from clipboard to replace the existing cbz,
- tidy up the 'data' folder.
BR