Here's how :

  $ sudo apt install poppler-utils pandoc
  $ for pdf in *.pdf; do pdftohtml -c -noframes "$pdf" "${pdf%.pdf}.html"; done
  $ for html in *.html; do pandoc "$html" -o "${html%.html}.epub"; done

For your convenience :

https://files.web.dynu.net/RCDtnceIVfyv.zip