simp
init₁ init₂ : ℕ
l₁ l₂ : List ℕ
x : ℕ
xs : List ℕ
y : ℕ
ys : List ℕ
h : List.length (x :: xs) = List.length (y :: ys)
⊢ foldl (fun a b => a + b) (init₁ + init₂) (zipWith (fun a b => a + b) (x :: xs) (y :: ys)) =
    foldl (fun a b => a + b) init₁ (x :: xs) + foldl (fun a b => a + b) init₂ (y :: ys)
init₁ init₂ : ℕ
l₁ l₂ : List ℕ
x : ℕ
xs : List ℕ
y : ℕ
ys : List ℕ
h : List.length (x :: xs) = List.length (y :: ys)
⊢ foldl (fun a b => a + b) (init₁ + init₂ + (x + y)) (zipWith (fun a b => a + b) xs ys) =
    foldl (fun a b => a + b) (init₁ + x) xs + foldl (fun a b => a + b) (init₂ + y) ys