Contradiction with Jeremiah 33:3
Isaiah 42:9 speaks of new things declared by God before they happen, while Jeremiah 33:3 emphasizes calling unto God for knowledge of great and mighty things which you do not know.
Jeremiah 33:3: Call unto me, and I will answer thee, and shew thee great and mighty things, which thou knowest not. [mighty: or, hidden]
Contradiction with Ecclesiastes 1:9
Isaiah 42:9 highlights new things God will do, whereas Ecclesiastes 1:9 suggests there is nothing new under the sun, implying continuity rather than novelty.
Ecclesiastes 1:9: The thing that hath been, it [is that] which shall be; and that which is done [is] that which shall be done: and [there is] no new [thing] under the sun.
Contradiction with Hebrews 13:8
Isaiah 42:9 mentions new things, whereas Hebrews 13:8 emphasizes the unchanging nature of Jesus Christ, suggesting constancy over new developments.
Hebrews 13:8: Jesus Christ the same yesterday, and to day, and for ever.
Contradiction with Malachi 3:6
Isaiah 42:9 talks about new things coming to pass, but Malachi 3:6 states that the Lord does not change, implying no new actions or changes.
Malachi 3:6: For I [am] the LORD, I change not; therefore ye sons of Jacob are not consumed.