How to express ‘one of the most difficult things’  in Mandarin Chinese?

‘one of the most difficult things’  in Mandarin Chinese should be:

· 最具挑战性的事情之一
Zuì jù tiǎozhàn xìng de shìqing zhī yī
One of the most challenging things
· 最难的事情之一
Zuì nán de shìqing zhī yī
One of the hardest things

例句:

· Learning a new language is one of the most difficult things.
学习一门新语言是最困难的事情之一。
Xuéxí yì mén xīn yǔyán shì zuì kùnnán de shìqing zhī yī.