Oh variables

Algebra Level 2

$\large \frac{\color{#D61F06}{x}}{\color{#D61F06}{x}-\color{#3D99F6}{z}} + \frac{\color{#3D99F6}{z}}{\color{#D61F06}{y}-\color{#3D99F6}{z}}$

If $\color{#D61F06}{x} + \color{#D61F06}{y} = 2\color{#3D99F6}{z}$ and $\color{#D61F06}{x} \ne \color{#3D99F6}{z},$ find the value of the expression above.