simp [h, DifferentiableOn]
z z₀ : ℂ
U : Set ℂ
hp : has_primitives U
hU : IsOpen U
hU' : IsPreconnected U
h : U = ∅
f : ℂ → ℂ
⊢ DifferentiableOn ℂ f U → (∀ z ∈ U, f z ≠ 0) → ∃ g, DifferentiableOn ℂ g U ∧ EqOn f (cexp ∘ g) U
no goals