Judah ... Israel ... together - (Isa 11:12, Isa 11:13; Jer 3:18; Eze 34:23; Eze 37:16-24).
one head - Zerubbabel typically; Christ antitypically, under whom alone Israel and Judah are joined, the “Head” of the Church (Eph 1:22; Eph 5:23), and of the hereafter united kingdom of Judah and Israel (Jer 34:5, Jer 34:6; Eze 34:23). Though “appointed” by the Father (Psa 2:6), Christ is in another sense “appointed” as their Head by His people, when they accept and embrace Him as such.
out of the land - of the Gentiles among whom they sojourn.
the day of Jezreel - “The day of one” is the time of God’s special visitation of him, either in wrath or in mercy. Here “Jezreel” is in a different sense from that in Hos 1:4, “God will sow,” not “God will scatter”; they shall be the seed of God, planted by God again in their own land (Jer 24:6; Jer 31:28; Jer 32:41; Amo 9:15).