The simplest way to combine geometries is to use the GeometryGroup and
nest the other Geometry-derived objects inside. Here’s an example that
places an ellipse next to a square.

The effect of this markup is the same as if you supplied two Path elements,
one with the RectangleGeometry and one with the EllipseGeometry (and
that’s the same as if you used a Rectangle and Ellipse shape instead).
However, there’s one advantage to this approach. You’ve replaced two
elements with one, which means you’ve reduced the overhead of your user
interface. In general, a page that uses a smaller number of elements with
more complex geometries will perform faster than a page that has a large
number of elements with simpler geometries. This effect won’t be apparent
in a page that has just a few dozen shapes, but it may become significant in
one that requires hundreds or thousands.