How to get a common coordinate from two different coordinates on Elliptic Curves?

Question

I am trying to write a SageMath script that multiplies two coordinates on Elliptic Curves into one common coordinate.

SageMath Elliptic curves over finite fields documentation

p = Number
M1 = EllipticCurve (GF (p), [0,7])
C1 = M1 ([x1, y1])
C2 = M1 ([x2, y2])
C3 = C1 * C2

Somewhere they wrote that using sets of the SageMath function it is possible to do this. How to do it?