The Zero Constraint

Algebra Level 3

$\large \dfrac1{a^2 + b^2 - c^2} + \dfrac1{a^2 - b^2 + c^2} + \dfrac1{b^2-a^2+c^2}$

If $a,b$ and $c$ are non-zero such that $a+b+c=0$ , find the value of the expression above.