I got one of these:
https://www.roofbox.co.uk/scripts/rbvehsel4_tab.php/car-specific-accessories/atera_strada_sport_m_2_to_3_bike_carrier_no_ar2684/Qx%40w%2C6M42VAwp3%40Rb%7B%7EcC4ure5CWYj
Very happy with it. The carrier locks onto the tow bar and the bikes lock onto the carrier. Easy to get on and off and the assembly slides away from the car to allow access to the tail gate. Worked fine for me on our recent rip to the Northumberland. Very sturdy - doesn't move at all, even at high speed and/or over bumps. (It was for the Discovery, not the Zed!)