1)
What do we learn from "b'Za'am Titz'ad Aretz"?
1.
Rashi: He will trample the land with anger to expel the seven Kena'ani nations.
2.
Malbim: The verse teaches that in this aspect, salvation (personified) does not ride on Hashem's chariot to save. Hashem will do so Himself. He will trample with anger and Midas ha'Din, and thresh Goyim with anger.
2)
Why does it add "b'Af Tadush Goyim"?
1.
Radak: The matter is repeated in different words.
