In what way do [all trees of Levanon] not suffice to burn?
Rashi #1: On His Mizbe'ach 1 .
Rashi #2: It does not suffice to atone for the nations' sin. Radak: The nations who think that I cannot take Yisrael from them - no Olah that they will offer to Me will atone for them, after they see that I take them out, and they regret their words. Levanon is a forest in Eretz Yisrael.
Malbim: "Secharo Ito" (10) - the nations cannot offer a bribe of Korbanos that will entice Him to change His desire - "Lo Ekach mi'Beisecha Far...; Ki Li Kol Chayso Ya'ar" (Tehilim 50:10), "ha'Yirtzeh Hashem b'Alfei Eilim" (Michah 6:7).
Perhaps this means that they do not suffice to keep the fire going. (PF) Shamayim's fire consumes very quickly (Rashi Zevachim 59b DH Elef).
What is the meaning of "v'Chayaso Ein Dei Olah"?
Rashi #1: All the animals of Levanon are not enough [for His Mizbe'ach] 1 .
Rashi #2: All the animals of Levanon do not suffice to atone for the nations' sin.
Refer to 40:16:1:1*.