2D oscillator

$H\_0=\frac{P\_x^2}{2m}+\frac{P\_y^2}{2m}+\frac{1}{2}m\omega^2\left(x^2+y^2\right)$

with perturbation

$H\_1=h\omega \left(\frac{L\_z^2}{h}-2\right)$

How to write the perturbation in terms of the creation-annihilation operators?
This is different and I don't know how to deal with $L\_z^2$