What is the meaning of "Mi Siken Es Ru'ach Hashem"?
Rashi citing Targum Yonasan: Who put Ru'ach ha'Kodesh in the mouths of the Nevi'im? Hashem did - He is proper to fulfill [His words]!
Rashi: Who prepared Hashem's Ru'ach?!
Radak: When He did all this, who prepared His Ru'ach? This is like "v'Nafsho Ivsah va'Ya'as" (Iyov 23:13). No angel, and surely no man, could prepare His Ru'ach and inform His counsel when He made the world, and tell Him 'do like this' - "Noteh Shamayim Levado" (44:24)!
Radak (12): Refer to 40:12:6:3.
Malbim: Who prepared wind, the fourth 'element' (earth, fire, water and air)? Since Hashem made the elements, all the more so He has great power over what is composed of them, i.e. the entire physical creation. Who can stand against His ability?!
Why does it say "v'Ish Atzaso Yodi'enu"?
Rashi citing Targum Yonasan: Hashem makes known His Ru'ach to His confidants (Tzadikim).
Rashi: It seems that v'Ish Atzaso refers to the start of the verse. Who is His counselor, who gives counsel to Hashem?! Radak - "Mi" applies also to this.