What is the meaning of "v'Yashiru"?
Radak: They will say song and praise to Hashem, and sing about His awesome ways and deeds. Everything is in His hand, to lower or raise.
How is "Gadol Kevod Hashem"?
Radak: He alone is Kel. When David became king, it says "va'Yetzei Shem David b'Chol ha'Aratzos va'Shem Nasan Pachdo Al Kol ha'Goyim" (Divrei ha'Yamim I, 14:17). In their fear of him, they feared Kel, for they knew that he [became king] via Hashem. Via this, they admitted to Hashem, that He is Master over everything. He made David king after all despaired from him. And so Chiram Melech Tzor sent to Shlomo "Baruch Hashem Elokei Yisrael Asher Asah Es ha'Shamayim v'Es ha'Aretz Asher Nasan l'David ha'Melech Ben Chacham" (Divrei ha'Yamim II, 2:11). From the greatness of David and his kingship, Chiram admitted that Hashem made Shamayim va'Aretz.
Malbim: His honor depends on Himself; it is not reduced if He oversees lower beings.
