cases b
case mk
b c : ℤα
z✝ w✝ : ℤ
⊢ toℂ (mul { z := z✝, w := w✝ } b) = toℂ { z := z✝, w := w✝ } * toℂ b
case mk.mk
c : ℤα
z✝¹ w✝¹ z✝ w✝ : ℤ
⊢ toℂ (mul { z := z✝¹, w := w✝¹ } { z := z✝, w := w✝ }) = toℂ { z := z✝¹, w := w✝¹ } * toℂ { z := z✝, w := w✝ }