If $$x - y + z = 0$$, then find the value of $$\frac{y^{2}}{2xz}-\frac{x^{2}}{2yz}-\frac{z^{2}}{2xy}$$

A

$$\frac{3}{2}$$

B

$$\frac{1}{2}$$

C

-6

D

$$-\frac{3}{2}$$