ZF mount is different where it attaches to the back end of the gearbox. looks the same but the dimensions are different
Just so, like DanC states. The metal mount specific for the ZF is not available from Mercedes however.
ZF made a repro part in conjunction with the production run of the ZF S5-20 boxes (in 2011), to enable them to supply together with the new box to their customers. So, you can ask them about it. See it here on picture attached (from ZF mounting instruction 2011).
Also see advertising flyer from 2011