1) Download mp3 files to computer.
2) Open iTunes music library.
3) Drag-drop mp3’s onto library or use Add file to library.
4) Plug phone into computer, wait for sync to complete.
5) Drag-drop files from iTunes to your iPhone.
6) Files can be found in Music, listen to lectures at your leisure.
I have not downloaded a zip-pack, once downloaded and unzipped, I would think the same process would apply.