in pronouncing Mozart as Mote-zart instead of Mo-zart?

I, also, used the same pronunciation that you favour, wow, for many, many years. My Afrikaans-speaking friend at Oxford slapped my wrist (literally, not metaphorically!) every time I did so, and insisted it was Mo -tzart. Indeed, when I started to learn German (also at Oxford), I was taught that the letter "z" was pronounced "tz."

So - I now call Wolfgang, the beloved of God, "Mo-tzart" and I guess shall do so for the rest of my natural.