From: Farley Flud <ff@linux.rocks>
Subject: Re: Something I Never Fucking Knew
Newsgroups: comp.os.linux.advocacy
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Date: Sun, 23 Jun 2024 10:57:22 +0000
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On Sun, 23 Jun 2024 10:39:54 +0000, Farley Flud wrote:

> 
> It seems that the EPUB contains some sort of extra data that
> will distinguish it from an ordinary zip file.
> 

That extra data is an uncompressed MIME type block.

So the ZIP format is not actually a pure ZIP format.

This also explains why an EPUB can't be unzipped, edited,
and then zipped again.  The result will not be an EPUB.