Does "Efrayim" refer only to Shevet Efrayim?
Radak: No, it is all of Yisrael other than Yehudah.
Who are "Tzorerei Yehudah"?
Radak: They are people of Yehudah who pained Efrayim, for some of Efrayim envied Malchus Beis David and were enemies to them. We find that David reigned over Yehudah alone for seven years; only after, he reigned over all of Yisrael. Also when he returned to kingship after fleeing Avshalom, Yisrael said "Genavucha Acheinu Ish Yehudah", "va'Yikash Davar Ish Yehudah mi'Dvar Ish Yisrael", "va'Yiska [Sheva ben Bichri] ba'Shofar" (Shmuel II, 19:42, 44, 20:1). [There was enmity] until the kingship was divided when Rechav'am said "Ani Osif Ol Aleichem" (Melachim I, 12:14).
Malbim: They are not those of Efrayim who envied Malchus Yehudah; they did not pain them. Rather, they are from other nations.
What is the meaning of "Yichresu"?
Radak: There will not be (it does not mean that they will die). The same applies to "v'Nichresah Keshes Milchamah" (Zecharyah 9:10).
Why does it say that there will be no envy between Efrayim and Yehudah?
Rashi: Mashi'ach ben Yosef and Mashi'ach ben David will not envy each other.
Radak: There was envy between them in their exile. Efrayim envied Malchus Beis David.
Malbim: Initially, Efrayim envied Yehudah when the entire kingship was in Yehudah. Efrayim thought that Yehudah deprives it of the kingship that it deserves. Yehudah afflicted Efrayim for rebelling against Malchus David. Now they will know that kingship belongs to Beis David, and they will not envy each other.
