Therefore, see, I will proceed to do a marvelous thing among this people, wonder after wonder

"Therefore, look and see! I am going to do wonderful and marvelous things among you that you will not be able to explain"

The wisdom of their wise men will perish, and the understanding of their prudent men will disappear

Both of these statements mean the same thing. Yahweh showing that the wise people cannot understand or explain what Yahweh does is spoken of as if their wisdom and understanding will vanish. (See: rc://en/ta/man/translate/figs-parallelism and rc://en/ta/man/translate/figs-metaphor)