It was hard to tell the difference between the two versions.

很难分辨出这两个版本有什么区别。

《牛津词典》

Sometimes, it can be hard to tell the difference.

不过有时候，确实很难分辨其中的差异。

youdao

It is hard to tell the difference between the two versions.

很难分辨出着两个版本有什么区别。

youdao

It even, I think, identifies the divine and the human, makes them hard to tell apart;binds them, even while we are being confronted with their difference.

我想，甚至这，使圣与人，难以被分辨，把他们联结在一起，尽管我们也看到,圣与灵之不同。

耶鲁公开课 - 现代诗歌课程节选

Dr Connolly acknowledged it was sometimes hard to tell the difference between harmless slagging and racist abuse.

BBC: Racist graffiti

But the market also seems to have penalised some good firms as well as bad (though since so few new technology companies make money, it is often hard to tell the difference).

ECONOMIST: Have the markets really punctured the dot.com bubble?

Truly, you'd be hard-pressed to tell the difference.

ENGADGET