A = X1
B = Y1
C = Z1*X2
D = Z1*Y2
E = A*B
F = C*D
G = E+F
H = E-F
t0 = A-C
t1 = B+D
t2 = t0*t1
J = t2-H
t3 = A+D
t4 = B+C
t5 = t3*t4
K = t5-G
X3 = G*J
Y3 = H*K
t6 = J*K
Z3 = k*t6