Tomamos como el límite
$$\lim_{x \to 0^+}\left(\frac{z^{2} x^{2} y^{2}}{z^{6} + \left(x^{6} + y^{6}\right)}\right)$$
cambiamos
$$\lim_{x \to 0^+}\left(\frac{z^{2} x^{2} y^{2}}{z^{6} + \left(x^{6} + y^{6}\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{x^{2} y^{2} z^{2}}{x^{6} + y^{6} + z^{6}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{x^{2} y^{2} z^{2}}{x^{6} + y^{6} + z^{6}}\right) = $$
$$\frac{0^{2} y^{2} z^{2}}{y^{6} + z^{6} + 0^{6}} = $$
= 0
Entonces la respuesta definitiva es:
$$\lim_{x \to 0^+}\left(\frac{z^{2} x^{2} y^{2}}{z^{6} + \left(x^{6} + y^{6}\right)}\right) = 0$$