1)
Why does it say "Zamru Elokim"?
1.
Radak: This is like [Zamru] lEi'lokim (sing to Him).
2)
Why is "Zamru" repeated?
1.
Radak: This is to strengthen the matter.
2.
Malbim: Refer to 47:7:3:2.
3)
Why does it say "l'Malkeinu"?
1.
Radak: After it said that He is a great King over the entire land, His name was designated on us in the world, and He is our King from then, but on that day He will be King over the entire land.
2.
Malbim: Malkeinu refers to Shem Havayah (refer to 47:6:1:4); sing to the elevation [of Elokim, and also] of this name.
