Contradiction with Jonah 3:10
This verse shows God sparing Nineveh after they repented, whereas Zephaniah 2:13 foretells Nineveh's destruction.
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 Jeremiah 18:7-8
God states He can relent from destroying nations if they repent; Zephaniah 2:13 predicts unavoidable destruction.
Jeremiah 18:7-8: [At what] instant I shall speak concerning a nation, and concerning a kingdom, to pluck up, and to pull down, and to destroy [it];