Do not waste your breath.

不要浪费口舌了。

He won't listen, so don't waste your breath on him.

他不会听你的，别枉费唇舌了。

It's no use talking to him, you'll only waste your breath.

和谈谈话没有一点用处，你只是在白费唇舌。

It's no use talking to him. You'll only waste your breath.

和他谈没用，你只会白费唇舌。

They won't listen, so don't waste your breath telling them.

他们听不进去，不必和他们白费唇舌了。

Don't waste your breath try to convince him; he's going to leave anyway.

不要白费口舌劝阻他了，他反正也要走的。

He won't take the exam, so don't waste your breath trying to persuade him.

他不会应试的，所以不要白费唇舌地试图劝他了。