While I have never used the Arca Swiss Z1, I have a Markins M10 on my series 2 Gitzo and it is a perfect match. What sold me on the Markins was the "Sweet Spot". Once I set it, I could then move my camera to different positions without having to turn a knob and it stays in place.
I am not sure I understand why you would opt for a RRS clamp when the one that comes on the Markins will fit the RRS L-plate with no problem. I have the knob screw type and use a Kirk L bracket with no problem.
Jerry Jaynes Great Smoky Mountains of North Carolina