have : Even a.re ↔ Even a.im := by
  have : ¬ Even (3 : ℤ) := by decide
  simpa [this, Zsqrtd.norm_def, parity_simps] using heven
a : ℤ√(-3)
hcoprime : IsCoprime a.re a.im
heven : Even a.norm
⊢ ¬Even a.re ∧ ¬Even a.im
a : ℤ√(-3)
hcoprime : IsCoprime a.re a.im
heven : Even a.norm
this : Even a.re ↔ Even a.im
⊢ ¬Even a.re ∧ ¬Even a.im