Rashi writes on Bamidbar 30:2:
“Zeh haDavar — This is the Idea“: Moshe gave nevu’ah with “Koh amar Hashem — Like this said Hashem, ‘Like in the middle of the night'” (Shemos 11, about Makas Bekhoros). And the nevi’im prophesied with “Koh amar Hashem“. Moshe was beyond them in that he also prophesied in the language of “Zeh hadavar — This is the Idea”.
The precision of “zeh“, this. Other nevi’im lacked the clarity of being able to say “zeh“, this is exactly what Hashem said. Instead they said “koh“, something like, approximately.
The Torah reading on the last day of Chanukah opens “Zos Chanukas haMizbeiach“, words that lend today its traditional name “Zos Chanukah“.
Chanukah progresses — one candles, two candles… More light and more light. We get beyond the limitations of this world when we go from day 7 to day 8. When we transition from the week of creation to our calling to go beyond creation, to partner with Hashem to complete His Work.
It is the eighth day when we reach chinukh, establishment, inauguration. Chunakas haMizbeiach, inaugurating the altar where flesh is dedicated to avodas Hashem. Where we introduce something otherworldly into this universe.
And that’s the day, the eighth day when we can reach the clarity of Zos Chanukah.