So while I would have loved to be a writer, that was not my Muse. I became a Chemical Engineer instead [BS & PhD at Cal, go Bears] and had to make do with no Muse at all. I did learn the scientific experimental method though and thought I would apply it.

Someone recently uploaded an illustrated version of Kim by Kipling here that seemed likely to pass epubcheck.

Step 1. Download that epub file an run epubcheck on it. As expected no errors or warnings.

Step 2. Decompress this file using 7-Zip and then compress that back into an epub file using the procedure described in my previous post.

Step 3. Run epubcheck on the file from step 2. Result:

So that's interesting. How do others do the compression, with what program?

Note changed file names to Kim.epub & Kim2.epub