Think you might need one of these adaptors for the round siver coax cable you have there (DSP cable).
https://www.amazon.co.uk/dp/B077JKX1WJ/ref=cm_sw_r_cp_apa_i_U40pDbKPXZ21R/?tag=z4fo-21
Also take a look at this thread for more info...
https://z4-forum.com/forum/viewtopic.php?f=31&t=116477&p=1672268&hilit=Cd+changer+connections#p1672268