http://opengreekandlatin.github.io/csel-dev/ http://opengreekandlatin.github.io/english_trans-dev/
I think it would make sense to implement the epub export functionality as part of DiogenesWeb, since it already has code to convert the XML of Diogenes/Perseus, etc. to HTML. It is written in Node/Javascript, and it seems that there is an epub creation library: https://github.com/bbottema/js-epub-maker