[axu2]

I see, the ToC looks fine in EPUBs for Koreader. But CBZ doesn't preserve the original names. That's definitely a problem.

What's the advantage of using Koreader over the built in Kindle software?

At this point, it's probably better to ask the Koreader devs to add natural sort for internal cbz folders. Renaming things has caused many issues for KCC in the past, so many page order issues.