I would suggest M4B support , see : http://forums.sandisk.com/t5/Clip-Zip/MB4-Support/td-p/264197
According to http://wiki.librivox.org/index.php/How_To_Make_M4B_Files it says “An M4B file is an audio file which can be bookmarked. This is the audio-book file type.”
In the case (“this is the audio book file type”) is true AND (“zip supports audio book file type”) is true –> M4B support should be true
(I am aware that other digital formats are ALSO able to store audio like spoken text… but refer to “THE” audio book file type)
