The green solid block is bored at the same angle (α = 90 deg.) of the shafts and centers of the bores at a distance apart equal to the difference in the plane of shaft alignment.
It is constant velocity coupling.
The blue ellipse is locus of center point of the green block. It is in bisectional plane of two vertical planes containing shaft axes.
In term of movable joints the mechanism is similar to a planar Oldham coupling.
If α = 0 deg the mechanism turns into a planar parallelogram (rhombus) one.