The customs of the people are vain - חקות chukkoth; the statutes and principles of the science are vain, empty, and illusory. They are founded in nonsense, ignorance, idolatry, and folly.
One cutteth a tree out of the forest - See the notes on Isa 40:19 (note), and Isa 44:9 (note), etc., which are all parallel places and where this conduct is strongly ridiculed.