Let \( \mathbb{C} = \{ z = x + iy : x \text{ and } y \text{ are real numbers}, i = \sqrt{-1} \} \) be the set of complex numbers. Let the function \( f(z) = u(x, y) + i v(x, y) \) for \( z = x + iy \in \mathbb{C} \) be analytic in \( \mathbb{C} \), where
\[
u(x, y) = x^3 y - y x^3 \quad \text{and} \quad v(x, y) = \frac{x^4}{4} + \frac{y^4}{4} - \frac{3}{2} x^2 y^2.
\]
If \( f'(z) \) denotes the derivative of \( f(z) \), then: