Why does it say "Hashem mi'Marom Yish'ag"?
Malbim: Roaring is louder than merely raising the voice. Mi'Marom refers to conduct via the Ma'arachah, which is in Shamayim. This is constant, so He constantly roars there. Now He will roar very loud.
What is the significance of "umi'Ma'on Kadsho"?
Malbim: This refers to conduct via Hashgachah, which is above the Ma'arachah.
Why does it say "Al Navehu"?
Rashi: [Hashem mourns] the Churban of His house.
Radak: This is a metaphor - it is as if Hashem will roar loudly, and the Goyim will hear and come to destroy His residence, i.e. the Beis ha'Mikdash.
What is the meaning of "Heidad"?
Rashi: It is an expression of Hoy. People doing heavy work shout to invigorate each other. People who press [grapes] in winepresses regularly say so.
What is the meaning of "Ya'aneh"?
Rashi: This always means screaming loudly.
Malbim: Just like people who stomp in the winepress, one calls out and all answer, all who tear will answer the lion's roar (and come to help destroy the Mikdash.- PF)
