Young could possibly have pulled it off in Zaire. I think it's slightly unlikely,as Foreman would be cutting off the ring,and backing Jimmy on to the ropes constantly. Jimmy's punches would n't have the same impact on George as Muhammad's did. I can see George surviving a few rocky moments and stopping Young late in the fight. 1977 San Juan was the right place and time for Jimmy to beat George.
I don't think Jimmy had quite gotten going into his good stuff at the time of the Rumble. Foreman hadn't deterriorated like he did after Ali made a ****** of him. In 1974, October, Young was just about to get his close win that was scored a draw over Shavers. He would then gain confidence and school Lyle, and go on a tear. On that tear, he had the stuff to beat this Foreman. But not in October 1974. Foreman TKO8.