"The EPUB Publication's resources are bundled for distribution in a ZIP-based archive with the file extension .epub. As conformant ZIP archives, EPUB Publications can be unzipped by many software programs, simplifying both their production and consumption.
The container format not only provides a means of determining that the zipped content represents an EPUB Publication (the mimetype file), "
The EPUB format also adopted this convention: https://www.w3.org/publishing/epub3/epub-spec.html#sec-intro...
"The EPUB Publication's resources are bundled for distribution in a ZIP-based archive with the file extension .epub. As conformant ZIP archives, EPUB Publications can be unzipped by many software programs, simplifying both their production and consumption.
The container format not only provides a means of determining that the zipped content represents an EPUB Publication (the mimetype file), "