It appears that qxf to qdf conversion is foremost related to Quicken tax preparation software, especially considering both of these file types originate from it, although the first one is from Mac version and the other from the version for Windows.
It might be actually possible that Quicken can export/convert data from the Mac version (.qxf) to files for Windows platform (.qdf) and this should be not a problem even in latest versions of Quicken. Further information about how to convert qxf to qdf can be found as Quicken website.Open QXF file Open QDF file
A personal finance management program by Intuit
Mac version of popular Quicken personal finance management software
Financial and accounting software for Mac