  Consider the natural graph associated to a rhombus tiling of a polygonal
regionin the plane. The spin correlations between boundary vertices of this
graph inthe Z-invariant Ising model do not depend on the choice of the rhombus
tilingbut only on the region. We provide a matrix formula depending on the
regionwhich allows practical computations of boundary correlations in this
setting,extending the results of Galashin in the critical case.
