这个工程非常艰巨。

Zhège gōngchéng fēicháng jiānjù.

This project is extremely challenging.

老板说有一项艰巨任务要给我负责。

Lǎobǎn shuō yǒu yí xiàng jiānjù rènwu yào gěi wǒ fùzé.

The boss said there’s a tough task he wants me to take responsibility for.

这个项目的任务很艰巨，需要大家合作。

Zhège xiàngmù de rènwù hěn jiān jù, xūyào dàjiā hézuò.

The tasks of this project are challenging and require everyone's cooperation.