Why does it say "Hass Mipnei Hashem Elokim"?
Radak: Be silent due to Him. You thought that He will not look at your deeds. Be silent - soon will come the day when He will bring on you [payment for your deeds].
Malbim: These are the Navi's words. After mentioning Devar Hashem, he says that all should be silent, for His day is close.
What is the "Zevach"?
Radak: The dead bodies of the Resha'im.
Malbim: The decree was made.
What is the meaning of "Hikdish Keru'av"?
Rashi: He summonsed [Malbim - Nebuchadnetzar's] soldiers for the appointed day.
Radak: He summonsed the invitees for that Zevach, i.e. Ohf ha'Shamayim and Chayas ha'Sadeh to eat the dead bodies, like it says "v'Haysah Nivlasecha l'Ma'achal l'Chol Ohf ha'Shamayim ul'Vehemas ha'Aretz" (Devarim 28:26).