What is "Aven Efes"?
Metzudas Tziyon: These, and Ru'ach v'Sohu, all refer to something without any benefit.
Malbim: Refer to 41:29:2:2.
Why does it say "Hen Kulam Aven Efes"?
Rashi: You should know that all the Nevi'im who contradict Torah, all their deeds are Aven v'Efes.
Malbim: They themselves are Aven (of no substance), and their deeds are Efes - they cannot harm or help. These correspond to "v'Ere v'Ein Ish" and "ume'Eleh v'Ein Yo'etz", respectively.
What are "Niskeihem"?
Rashi: The form in which they were melted, like it says "ha'Pesel Nasach Charash" (40:19).
Radak: They melted and covered them with silver and gold for naught, for they do not help. They do not tell them anything about the future.
Malbim: It is their authority, or their idolatry. It itself is Ru'ach (futile), and it is Tohu regarding action - it cannot harm or help.
