Ich habs auch erst nicht verstanden, weil ich von phonetischen Alphabeten keinen blassen Schimmer habe. Ich vermute mittlerweile, dass es um eine sehr deutsch ausgesprochene Form des Wortes "Cousin" geht.
It's not [kuzɛ̃], but with ng as in "boing". Also unless we're talking loans or Occitan substrate there's no voiced velar nasal in French at all, in a language full of nasal everything.
In addition to what others already said: The French pronunciation is also accepted in Germany and in the view of many more prestigious. I once received bad reactions for using the one in the meme