Hello
There are 2 different headunits in a Zed, a non Bose and a Bose, neither of which are a Bose and both of which are woeful
There are lots and lots of threads on here about what you can do to improve it, I decided to replace everything but you can do it in stages... change the HU to get better functionality i.e. iPod etc, next change speakers and then maybe amps etc too....
I wouldn't worry too much about theft of radio's etc these days, if someone is going to break into a car they are looking for satnavs, tablets etc more than a DD stereo...