zinc-alloy robotic arm

That sounds like the wrong material to make high-precision industrial robots out of. Zinc alloy is softer and heavier than aluminum. The only reason it's used for anything is because it's cheap and melts at a low temperature, so it's used to make cheap die cast metal parts like carburetors. And you could get similar results to the sculptures show with a 5-axis CNC machine made of cast iron, you don't need a robot arm.

He approached a life-size marble portrait of a topless woman — a present from the model’s husband for their poolside

:michael-laugh: