It seems so easy

Algebra Level 4

if $\frac { x }{ a } =\frac { y }{ b } =\frac { z }{ c }$ then $\quad { \left[ \frac { { a }^{ 2 }{ x }^{ 2 }+{ b }^{ 2 }{ y }^{ 2 }+{ c }^{ 2 }{ z }^{ 2 } }{ { a }^{ 3 }x+{ b }^{ 3 }y+{ c }^{ 3 }z } \right] }^{ \frac { 3 }{ 2 } }$ =

(the problem is not original)