Marcello Mastroianni should have played Zeller
I think he was more suited to the role than Richard Harris, for a number of reasons:
1) Mastroianni didn't need to be dubbed.
2) I thought Harris, at 33, was too young for the role. Mastroianni would have been 39, which is more suitable.
3) Harris is unconvincing as an industrialist, he tends to play physical roles.
4) Mastroianni is a better actor.
5) By casting Mastorianni, they could have dispensed with the unusual character name of Corrado Zeller and just used an Italian name.