Right now the format is extremely important because it is the only path to go from CHM to LaTeX... going from CHM to HTMLZ with Calibre and then using Pandoc to get from HTML (single file) to LaTeX.
At the moment one has to unpack the produced HTMLZ by hand and then proceed with the Pandoc translation because Pandoc only understands HTML, but we are in the process of writing an HTMLZ reader for it and then the translation process should be more automatic.
That is why it is so important to get the "specs" set down.
The format is starting to spread, check:
https://cloudconvert.org/htmlz-to-epub
or maybe this is powered by Calibre ...
Paulo Ney