Target rome's uranium supplies so that he can't build nukes. After you raze all of those cities, it's likely that Greece will expand into that territory. Why don't you keep some of the cites? If distance was so much of a problem why did you colonize the new world? Can every civ build nukes? After you've eliminated rome, go after the one that don't. As Rome's territory shrinks, they'll lose their vassals. If you have PA enabled, try to negotiate one with Alexander. Do you have a specific victory condition in mind yet? Depending on your relations with rome's vassals, you could get a diplomatic victory.