Question 802368
{{{(x^-4+y^-2)/(x^-6+y^-4)}}}

I am pretty sure that
{{{(1/x^4+1/y^2)/(1/x^6+1/y^4)}}}
is as far as you can go.

Check this link.
http://www.wolframalpha.com/input/?i=%28x^-4%2By^-2%29%2F%28x^-6%2By^-4%29+