A camp Ex. meeting at
Jack Z's house
A "camp Ex. meeting" likely means an executive meeting of Papa's chapter, or camp, of B'nai Zion (a.k.a. Order Sons of Zion) the Zionist fraternal order to which he belonged. His camp had formed just nine months earlier and went by the nickname "The Maccabean," a reference to the Jewish warrior heroes of the Hanukkah story. Papa had fought for the nickname, believing it conveyed an image of strength and competence, in the same eventful meeting in which he was elected Master of Ceremonies.
Papa's B'nai Zion brothers were also some of his best friends; "Jack Z." is, as our regular readers know, none other than the legendary Jack Zichlinsky, whose home on Brooklyn's Hart Street saw many a visit from Papa. I expect Papa had just hung out with a lot of his camp brothers on the previous day, too, when he attended a reception for the Zionist leader David Yellis at the Hotel Astor.