The sacrificing of an ox to Zeus here marks this god as the ultimate hymnic subject of the festive performances starting with the three songs of Demodokos in Odyssey 8 and capped by the narrative of Odysseus himself in Odyssey 9–12. As we see most clearly in the Homeric Hymns, the invoked divinity who presides over a given festival is the hymnic subject of the hymn (MoM 4§82). We know from Pindar Nemean 2.1–3 that Zeus was the hymnic subject of the Homēridai, notional descendants of Homer, who performed the Iliad and Odyssey in relay (HPC 240, MoM 4§§99.4, 99.5). Accordingly, I interpret the sacrifice to Zeus here at O.13.024–025 as a signature, as it were, of the Homēridai. See also the comment that introduces Rhapsody 9.