What exactly, was Elazar charged with doing in connection with the items listed in the Pasuk?
Rashi, Ramban #1 and the Seforno: It was his job to determine which of the B'nei K'has would carry the oil for the Menorah, the Ketores, the anointing oil and the Minchas ha'Tamid when they traveled. 1
Ramban #2 (citing the Yerushalmi, Shabbos, 10:3): Elazar was actually in charge of carrying all four items. 2
Ramban: Which in turn, is cited by Rashi in Shabbos, 92b.
Ramban: Something that was humanly impossible, bearing in mind that the Ketores alone - which Moshe manufactured for an entire year - comprised 365 Manah (36,500 Shekalim) and the Shemen ha'Mishchah, 183 Lugin (1098 egg-volumes). But Elazar was superhumanly strong, like Ya'akov Avinu and Moshe and Aharon - because "Those who place their hope in Hashem, will have renewed strength" (Yeshayah, 40:31).
And what does "Pekudas Kol ha'Mishakan ... " incorporate?
Rashi, Ramban and Seforno: Elazar was also in charge of designating each member of the b'nei K'has 1 to his role in the Avodah and what he should carry when they traveled. 2 (Regarding the latter, they would receive it from him when they set out and return it to him when they encamped 3 [Ramban]). 4
Rashi: Whereas Isamar was in charge of Gershon and Merari.
Rashi: In connection with all that is mentioned above..
Ramban: Moreover, Elazar was overall in charge of the Levi'im, above the three respective Nesi'im of Gershon, K'has and Merari (Refer to 3:32:1:1*).