It is easy to learn paper-cutting but very difficult to make it perfect.

剪纸学起来很容易，但要做到完美却很难。

youdao

This is my dream, a simple dream, but very difficult to do.

这就是我的梦想，简简单单，虽然做起来很难。

youdao

It's based on the idea of mathematical "trap-door" functions, which are easy to compute in one direction but very difficult to compute in the reverse direction.

它所基于的理念是数学上的“trap - door”函数，它可以沿着一个方向轻松地进行计算，但是很难从相反的方向进行计算。

youdao

But getting food to Fort Sumter would be a very difficult job.

VOA: special.2009.08.06

And scientists have been working on this for years and there's been progress, but it's still a very difficult challenge.

科学家们对此已经研究很久了,并取得了进展,但仍有很大挑战

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

So it's very difficult, but what I come down to is that you just have to place your energy on your breath, and every time you notice your awareness drifts to somewhere else, you have to recognize this drift and let it go.

因此这很难，但我总结的方法是,只需要把能量集中到呼吸上，每次注意力不集中,飘到别处时，要意识到意识的涣散，并放手不管。

普林斯顿公开课 - 人性课程节选

"Offences of this nature are easy to commit but very difficult and very expensive to detect, " he said.

BBC: Jail for ?86,000 eBay sport fraudster Christian Cassidy

But we have to make a series of collective but very difficult decisions to get our fiscal house in order.

WHITEHOUSE: Press Briefing

It's simple to say, but very difficult to bring off, something that cannot be taught and really is hard to pin down, and it either works or it doesn't.

NPR: Conductor James DePreist