help with contour plot

Hi!

I am trying to plot a contour but it says that the matrix domensions does not agree, anyone who knows why?

The equation and the demands are:

And my code is:

(The picture above my code is what it is supposed to look like)

Answer 1

[Walter Roberson]

Your Z needs to be defined in terms of X and Y, not in terms of x and y.

[Hanna Sundling]

Thank you!