Ironically this did not render in Firefox on Android (just the spinner kept spinning) Worked in Chrome.
That said, epubs are great for reading books on mobile. The advantage for pdfs is that they contain highlights/notes, so you can directly import them into Zotero and all your annotations are there. For epub, you have to hope there is a way to export the annotations that are stored by the reader app, and then you have to process them further. Readera is a great reader for mobile that makes this possible. I'm currently working on a script that will convert an epub to pdf, extract the annotations from Readera, and mark them in the pdf. Then I can import the pdf into Zotero, while still retaining the great reading experience of epubs.