Contradiction with Genesis 6:6
This verse implies God's regret for having created humankind, which contrasts with the promise of doing good in Zechariah 8:15.
Genesis 6:6: And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
Contradiction with Exodus 32:14
Here, God repents of the evil He planned against His people, which shows a change of intention unlike the steadfast promise in Zechariah 8:15.
Exodus 32:14: And the LORD repented of the evil which he thought to do unto his people.
Contradiction with Jeremiah 18:8
This verse indicates that God may relent from the promised good if a nation repents, contradicting the commitment to do good mentioned in Zechariah 8:15.
Jeremiah 18:8: If that nation, against whom I have pronounced, turn from their evil, I will repent of the evil that I thought to do unto them.
Contradiction with Jonah 3:10
God changes his intention to bring evil upon Nineveh, showing the possibility of altering planned actions which contrasts with the assurance in Zechariah 8:15 of doing good.
Jonah 3:10: And God saw their works, that they turned from their evil way; and God repented of the evil, that he had said that he would do unto them; and he did [it] not.
Contradiction with 1 Samuel 15:29
This verse indicates that God does not repent or change His mind, which contrasts with the idea of potentially altering intentions in other scriptures like Zechariah 8:15.
1 Samuel 15:29: And also the Strength of Israel will not lie nor repent: for he [is] not a man, that he should repent. [Strength: or, Eternity, or, Victory]