Contradiction with Genesis 1:31
Genesis 1:31 states that everything God made was very good, whereas Ecclesiastes 4:7 mentions vanity and emptiness observed under the sun, suggesting dissatisfaction.
Genesis 1:31: And God saw every thing that he had made, and, behold, [it was] very good. And the evening and the morning were the sixth day. [And the evening...: Heb. And the evening was, and the morning was etc.]
Contradiction with Matthew 6:19-20
Matthew 6:19-20 encourages storing treasures in heaven rather than earthly ones filled with vanity and emptiness like in Ecclesiastes 4:7.
Matthew 6:19-20: Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and where thieves break through and steal:
Contradiction with Philippians 4:11
Philippians 4:11 speaks of being content in all circumstances, contrasting with the theme of toil being vanity in Ecclesiastes 4:7.
Philippians 4:11: Not that I speak in respect of want: for I have learned, in whatsoever state I am, [therewith] to be content.
Contradiction with Romans 8:28
Romans 8:28 tells of all things working together for good, whereas Ecclesiastes 4:7 speaks of vanity and futility without mentioning a divine purpose.
Romans 8:28: And we know that all things work together for good to them that love God, to them who are the called according to [his] purpose.