The difficulties that would have to be encountered by any one who attempted to explore the Moon——assuming that it was possible to go there——would be incomparably greater than those that have to be faced in the endeavour to reach the summit of Mount Everest.
參考答案：

要點：該句的主干結(jié)構(gòu)是The difficulties...would be incomparably greater than those...。兩個破折號之間的部分是插入語，修飾who引導的定語從句。those指代difficulties。不定式短語to reach...修飾the endeavour。

譯文：對于任何試圖探索月球（假定到月球是可能的）的人來說，他們要遇到的困難之大，絕非攀登珠穆朗瑪峰遇到的困難可以比擬的。