I did a service on a zf 5hp18 and used castrol transmax z. It's done several thousand Ks now without fault. Its actually much more smooth than the original fluid. The box was on a 94 car, so it was before they started labeling the fuild as "lifetime" fluid.
I have done the same to my 98 318is, which is "lifetime" fluid, but it is a manual box and I used Redline MTL. Same good results on it.