Let \( f : \mathbb{R}^2 \to \mathbb{R} \) (where \( \mathbb{R} \) is the set of real numbers) be defined by
\[
f(x, y) =
\begin{cases}
\frac{(x - y)^3}{x^2 + y^2}, & (x, y) \neq (0, 0) \\
0, & (x, y) = (0, 0)
\end{cases}
\]
If \( f_x(0, 0) \) and \( f_y(0, 0) \) denote partial derivatives of \( f \) with respect to \( x \) and \( y \) at the point \( (0, 0) \), respectively, then \( f_x(0, 0) \) and \( f_y(0, 0) \), respectively, are:
