NET
4 Then I considered all the skillful work that is done: Surely it is nothing more than competition between one person and another. This also is profitless—like chasing the wind.
Darby
4 And I saw all labour, and all success of work, that it is man's jealousy of his neighbour. This also is vanity and pursuit of the wind.
KJV
4 Again, I considered all travail, and every right work, that for this a man is envied of his neighbour. This [is] also vanity and vexation of spirit.