source 2007 Feng--Wu, second JQN2 doubling formula, plus substitution epsilon=1, plus substitution delta=-a
appliesto 2xyz
parameter a2
assume a2 = 2 a
compute T1 = (X1 Z1)^2
compute T2 = Y1^2
compute S1 = (T2+2 c T1)^2
compute U = (X1 Z1+Y1)^2-T1-T2
compute V = U^2
compute X3 = U
compute Y3 = S1-c V
compute Z3 = T2-a2 T1-2 X1^4