use 0
case intro.intro.refine'_1
R : Type u_1
inst✝ : CommMonoidWithZero R
l : Multiset R
⊢ ∃ f, (∀ b ∈ f, Prime b) ∧ Associated (Multiset.prod f) 1
case h
R : Type u_1
inst✝ : CommMonoidWithZero R
l : Multiset R
⊢ (∀ b ∈ 0, Prime b) ∧ Associated (Multiset.prod 0) 1