First of all, thanks for your service. I wish I knew more about this subject, but I personally haven't even done this mod to my cdr 220, as I'm still living in the dark ages using the CD player. Lol. I don't know what a Zune is, but assume it's still an MP3 player? Maybe check out the Becker site link I show below. Becker makes the CDR 220, and they have a service center in NJ:
http://www.beckerautosound.com/parts/cable_part_number.html
They sell an Ipod and AUX cable. Maybe that can help you. Hope others more knowledgeable about this can chime in to help too. Good luck.