It is hard (difficult) to believe that ... 实在难以相信某事

可以用来表达非常难以相信的事实，在 that 后面加主语+动词来表达难以置信的事实就可以了，也可以单单用 (It's) Hard to believe!

例句：

It's hard to believe they didn't come to work.

实在无法相信他们居然没上班。

Why do you find it so hard to believe?

为什么你觉得那件事不可信呢？

You may find this very hard to believe, but it's true.

你可能觉得难以置信，不过这是事实。

对话：

A: It's hard to believe Natalie left.

娜塔莉离开了，真是难以置信。

B: I wish that she was still here.