It is difficult to convey the sheer complexity of the situation.

难说清楚形势究竟有多复杂。

The plan's success was balanced on a knife-edge.

计划能否成功还难说。

It was nip and tuck as to which boat would reach port first.

两条船中哪一条先进港都难说。

It is a tossup whether we shall get there in time.

我们是否能及时赶到那里还难说。

He's a hard nut to crack.

他是个难说服的人。

There's no telling what may happen.

难说会发什么事。

We should get to London before 7 o’clock, but there’s many a slip ’twixt cup and lip.

我们应能在7点钟以前赶到伦敦，可是事情往往难说准。

But only one reminds me of the courage and persistence it takes to stay the course in the Shadowland.

难说哪一个对我最重要，然而，仅有一件能提醒我在阴影之地坚持下去所需要的勇气和坚韧神。

It is hard to say.

难说。

With so many reports to mislead one, it is hard to say at whose door the responsibility should be laid.

报告多得摸着头绪, 难说责任该由谁负。