No. To format shift a file you have to remove its DRM (encryption). Even if it is a DRMed ePub, you will need to remove its DRM to read it with Stanza.
See
Adobe ADEPT DRM for EPUB circumvented, and note that Adobe PDF ebooks are similarly circumventable with tools from the same source.
It almost certainly isn't legal to strip the DRM from lending library ebooks, but if you delete the ebook within the lending period you are at least confirming to the intent of the rights management.