Zilpah is referenced in the genealogy in Genesis 46:18. Bilah is cited a few verses later in verse 25 of the same genealogy. With that I think we can say Zilpah and Bilah are matriarchs. Wilda Gafney in her book Womanist Midrash writes movingly, albeit briefly, on Zilpah and Bilah.
Zilpah is referenced in the genealogy in Genesis 46:18. Bilah is cited a few verses later in verse 25 of the same genealogy. With that I think we can say Zilpah and Bilah are matriarchs. Wilda Gafney in her book Womanist Midrash writes movingly, albeit briefly, on Zilpah and Bilah.