1)
Who will declare "Ei Eloheimo"?
1.
Rashi #1: Hakadosh-Baruch-Hu will say to Yisrael 1 - 'Where are the gods that you worshipped!?' 2
2.
Rashi #2 (on Pasuk 43): The enemy will say 'Where is the G-d of Yisrael 3 ?"
1
See Sifsei Chachamim here and on Pasuk 43, note 4.
2
See Sifri on Pasuk 38.
3
Ramban: As in Tehilim, 115:2.
2)
What are the implications of "Tzur Chasayu bo"?