I’ve got the BMW approved and fitted kit - only Front camera on the Zed but integration is BMW approved so no cutting / splicing / piggy back / fiddling the harness. I went down that route as I bought both cars new and didn’t want any argument in fault scenario.
There is rear camera (BMW) in our 335 but in all honesty, the rear camera is rarely looked at other than the odd inquisitive look to ensure it still works as it should.
The installation is non intrusive and very neat in both the Zed and the 335 and I’m currently looking at the possible installation of the surplus rear camera into my Z