source 1998 Cohen--Miyaji--Ono "Efficient elliptic curve exponentiation using mixed coordinates", formula (10), plus common-subexpression elimination
compute XX = X1^2
compute YY = Y1^2
compute U = 8 YY^2
compute S = 4 X1 YY
compute M = 3 XX + T1
compute X3 = M^2 - 2 S
compute Y3 = M(S-X3)-U
compute Z3 = 2 Y1 Z1
compute T3 = 2 U T1
