All Audiobooks in the series, Cleaned, Have covers and metadata, commonly renamed, then all files are Zipped and renamed to .zab (zab = Zipped Audio Book)
Simply rename the .zab back to .zip and unzip to uncompress it
(Zipping is not for size... not all audiobooks are single mp3 files, some are chapterized or time sliced multiple files, have covers or playlists, or may be formats other than mp3 (like m4a or flac.... some systems also block zips, and some software (like my calibre) assume zips are ebooks)
Renaming to ZAB is so they can coexist with zips of ebooks and be added to library managers (like calibre)...
Most Library Managers "Assume" that zip's are archives of ebooks, This ZAB suffix lets them coexist in most ebook library managers
All Audiobooks in the series ALSO have covers (.jpg) AND metadata (.opf) with filenames consistant with the Audiobook itself (.zab)
The .opf file (Metadata) and the .jpg (cover) load into library managers (so you can have an Audiobook AND cover AND metadata in programs (like Calibre), looks like an ebook with a zab format but is actually an Audiobook)
note you can NOT use the add books from archive option, but you CAN simply add em by Drag'n'Drop em from a "file explorer" to a calibre library page.
a real neat way to use em is to use a free open sourced media player that plays zips (or zabs) (like the free/open source Vlc Media Player, download at www.vlcmediaplayer.org/download.html, and in the registry just tell it to play/open .zab with vlcplayer, click on the audiobook in calibre and it plays)
Since the Authors/series/title are the same for the Ebook series torrents (by the same name but with "Ebook Series" instead of "Audiobook Series") they can easily be merged in one calibre library and give you BOTH formats in one book