Not had any direct experience, but believe when these types of sensors were last discussed, we couldnt use them effectively as we have the crash bar across the rear bumper which interferes with them. Might be worth asking them if thats the case still. You basically have to make sure that there is no solid metal structure within 30cm of them IIRC which means to position them away from the crash bar, they wont be "looking" in the right direction as it will be right at the bottom of the bumper.
Surely you know how to park the Zed though Colin