source 2007 Bernstein--Lange
unified
parameter c2
assume c2 = 2*c
assume Z2 = 1
compute B = Z1^2
compute C = X1 X2
compute D = Y1 Y2
compute E = d C D
compute BB = B^2
compute EE = E^2
compute H = (Z1+B)^2-BB
compute I = (Z1+E)^2-EE
compute X3 = (H-I)((X1+Y1)(X2+Y2)-C-D)
compute Y3 = (H+I-2 B)(D-C)
compute Z3 = c2(BB-EE)
