### Filtering an expression: keeping only term with even power

In the expression
$$
x^2 y^2+x y^2+x^3y + x^4 y^4
$$
I would like to keep only the term where the variables have even power
$$
x^2y^2+x^4 y^4
$$

Is there a way to do it?

I look into this post.

But ~~once I get ~~the ~~operand, I don't see how to test ~~operands list doesn't retain the ~~exponent of each variable.~~exponent