Usage of hard as adverb and adjective
Please help me correct sentences below.

No matter how they are working hard, they won't get a promotion.

No matter how hard they are working, they won't get a promotion.

No matter how they are doing hard work, they won't get a promotion.

Question

Usage of hard as adverb and adjective
Please help me correct sentences below.

No matter how they are working hard, they won't get a promotion.

No matter how hard they are working, they won't get a promotion.

No matter how they are doing hard work, they won't get a promotion.

Answer

1.  do not use, ok grammatically, but sounds very strange
2. correct
3. No matter that they work hard, they won't get a promotion. (correct but unusual, not recommended)

Answer

I feel it sounds most natural to say, "No matter how hard they work, they won't get a promotion."

Or perhaps, "No matter how hard they are working, they aren't going to get a promotion."