What is the comparison to "Har Peratzim"?
Rashi citing Targum Yonasan: Like the mountains when Hashem's honor was revealed in the days of Uziyah ha'Melech, and the miracles done for Yehoshua in Meishar Giv'on
What is the comparison to "Emek Giv'on"?
Radak: Like the war of Yehoshua in Giv'on, which was a great wonder - "va'Yhumem" (Yehoshua 10:10), so He will confound Yisrael. They will not have strength to stand against their enemies. Emek Giv'on refers to what He did in Emek Ayalon and in Giv'on.
Malbim: This explains "veha'Masechah Tzarah k'Hiskanes" (20). If they will want to gather themselves and stand crowded in their place, Hashem will rain on them giant hailstones like He did to the Kena'anim in Emek Giv'on (Yehoshua 10:11). There is no covering above to protect them from the hail. They cannot flee, and they cannot remain in their place.
What is "Zar Ma'asehu"?
Rashi: It will appear foreign to you, for harsh punishments will come on you.
Radak: When Hashem will rise to do His strange act against Yisrael, they will say 'His act is strange', for He did not do so earlier.
Radak citing his father: In Har Peratzim and Giv'on, Hashem rose to help Yisrael, to take vengeance against their enemies. Now it will be opposite - He will take vengeance against Yisrael.
Malbim: Hashem will rise in Har Peratzim to do His deed. It will be strange and something people are not used to, even though earthquakes are natural.
What is "La'avod Avodaso [Nochriyah]"?
Rashi: To do his work, like farming.
Radak: The matter is repeated in different words. Zar and Nochriyah are the same, and Ma'asehu and Avodaso are the same. The Targum of Ma'aseh is Uvda.
Malbim: This is raining fire on them from Shamayim; it is supernatural. Therefore, it is called Avodah. It will never happen naturally, therefore it is called Nochriyah.
