$43-45$ Evaluate the integral by changing to spherical coordinates.

$44.{\displaystyle \underset{-a}{\overset{a}{}}}{\displaystyle \underset{-\sqrt[\phantom{2}]{a^2-y^2}}{\overset{\sqrt[\phantom{2}]{a^2-y^2}}{}}}{\displaystyle \underset{-\sqrt[\phantom{2}]{a^2-x^2-y^2}}{\overset{\sqrt[\phantom{2}]{a^2-x^2-y^2}}{}}}(x^{2}z+y^{2}z+z^3)dzdxdy$