convert(UniqueFactorizationMonoid.normalizedFactors_prod hx).symm
x : ℤ
hx : x ≠ 0
⊢ Associated x (2 ^ evenFactorExp x * Multiset.prod (oddFactors x))
case h.e'_4
x : ℤ
hx : x ≠ 0
⊢ 2 ^ evenFactorExp x * Multiset.prod (oddFactors x) = Multiset.prod (UniqueFactorizationMonoid.normalizedFactors x)