split an epub per chapters

An epub book has multiple chapters. What method to split it into multiple files, each of them consist one chapter, effectively?

For example as the following:

1) Find: <h2

2) Replace: <hr class="sigil_split_marker" /><h2

3) Then select Edit > Split at markers.

how split a mkv with subtitles

You can use mkvtoolnix, then go to -> output, and -> splitting -> by parts based on timestamps -> and there you can write the beginning and the end of the part you want extract (without spaces: like 1:02:07-1:04:40, for example).