I think the most amazing multi-course job was Baltusrol. When Tillinghast was awarded this commission in the late teens, the existing course had already held severla national championships. He was able to convince the board of directors that they didn't need to build one course, they needed to get rid of the one they had and build two BETTER ones in its place!
They agreed to this as long as he was able to keep 18 holes open for play at all times, and he managed to do this. What an accomplishment. Two new world-class courses that have stood the test of time and have both held numerous national championships amateur and professional as well as male and female!
And all he had to do was destroy what was considered, at the time, one of the great courses of the world!