1)
What is the difference between Melech and Moshel?
1.
Malbim: A Melech is via the nation's consent, that he is proper to rule. Moshel is by force. Hashem is Melech by Himself, because He created everything. Meluchah is intrinsic to Him; it does not depend on a nation's choice.
2)
What do we learn from the verse?
1.
Rashi: They will see that Meluchah and Memshalah return to You.
2.
Radak: Then the Goyim will recognize that Meluchah is Hashem's, and then He will rule over them - "v'Hayah Hashem l'Melech Al Kol ha'Aretz" (Zecharyah 14:9).
