1)
Why does it say "Ezrenu b'Shem Hashem"?
1.
Malbim: Our trust in Hashem is our help.
2)
Why does it say "Oseh Shamayim va'Aretz"?
1.
Radak: He makes Shamayim va'Aretz; He has power among upper and lower beings. He can help us and take us out of the trap, i.e. Galus.
2.
Malbim: (a) He makes nature, and what is above nature. Therefore our help was miraculous and via Hashgachah, and not natural.
