source 2007 Hisil--Carter--Dawson
compute A = X1^2
compute B = Y1^2
compute C = (2 c Z1)^2
compute D = (A+B)^2
compute E = 2(A+B)(A-B)
compute F = A C
compute G = B C
compute X3 = X1(E-(D-G))(D-G)
compute Y3 = Y1(E+(D-F))(D-F)
compute Z3 = Z1(E-(D-G))(E+(D-F))