I did a quick search for:
zip file flat view
and didn't find a similar topic.
If, using Directory Opus v12.6 as the default zip handler, I enter a zip file, change to Mixed flat view (No Folders), multi-select several but not all files (in my use case, the files happen to be sequential, so I'm selecting the first file, then while holding shift I select the last file), then whether I Control-C, Control-X, right-click and use the menu to Copy or Move, or just drag the multi-selected files to the parent folder (that the Zip file is in), after I get the prompt whether I want to Recreate the folder structure or Copy/Move to the same folder, only the very first file I selected is copied.
Possibly a separate issue, but when choosing Move even only this single file is copied, not moved, but I don't usually use this functionality so I haven't dug into it to see if there's some Setting or other reason why the file isn't Moved from within the Zip. To be clear, the first paragraph represents the problem I'm posting about.