rw [even_and_odd_factors' _, Multiset.prod_add, factorsOddPrimeOrFour, Multiset.prod_add, hm,
  Nat.mul_div_right _ zero_lt_two, Multiset.prod_replicate, Multiset.prod_replicate, pow_mul]
case intro
a : ℤ
ha : 0 < a
heven : Even (evenFactorExp a)
this : Associated (Multiset.prod (UniqueFactorizationMonoid.normalizedFactors a)) a
m : ℕ
hm : evenFactorExp a = 2 * m
⊢ Associated (Multiset.prod (factorsOddPrimeOrFour a)) (Multiset.prod (UniqueFactorizationMonoid.normalizedFactors a))
case intro
a : ℤ
ha : 0 < a
heven : Even (evenFactorExp a)
this : Associated (Multiset.prod (UniqueFactorizationMonoid.normalizedFactors a)) a
m : ℕ
hm : evenFactorExp a = 2 * m
⊢ Associated (4 ^ m * Multiset.prod (oddFactors a)) ((2 ^ 2) ^ m * Multiset.prod (oddFactors a))