rw [Nat.even_mul] at this
a : ℤ√(-3)
r : ℤ
hcoprime : IsCoprime a.re a.im
hcube : r ^ 3 = Zsqrtd.norm a
f : Multiset (ℤ√(-3)) := factorization' hcoprime
h1 : a = Multiset.prod f ∨ a = -Multiset.prod f
h2 : ∀ (pq : ℤ√(-3)), pq ∈ f → 0 ≤ pq.re ∧ pq.im ≠ 0 ∧ OddPrimeOrFour (Zsqrtd.norm pq)
hf : f = factorization' hcoprime
x : ℤ√(-3)
hx : x ∈ f
this : Even (3 * evenFactorExp r)
⊢ Even (evenFactorExp r)
a : ℤ√(-3)
r : ℤ
hcoprime : IsCoprime a.re a.im
hcube : r ^ 3 = Zsqrtd.norm a
f : Multiset (ℤ√(-3)) := factorization' hcoprime
h1 : a = Multiset.prod f ∨ a = -Multiset.prod f
h2 : ∀ (pq : ℤ√(-3)), pq ∈ f → 0 ≤ pq.re ∧ pq.im ≠ 0 ∧ OddPrimeOrFour (Zsqrtd.norm pq)
hf : f = factorization' hcoprime
x : ℤ√(-3)
hx : x ∈ f
this : Even 3 ∨ Even (evenFactorExp r)
⊢ Even (evenFactorExp r)