Answer:
$cos~x + cos~y$$\cos~x + \cos~y$
Solution:
Approximate the x and y intercepts of the loop as $\frac{\pi}{3}$ (since $2^{-\frac{8}{5}} \simeq \frac{1}{3.03}$). Then we need $h(\pm \frac{\pi}{3}, \pm \frac{\pi}{3}) = 1$, so to turn those $\pm\frac{\pi}{3}$s into something reasonable we probably need $cos~x$$\cos~x$ (there are other ways, of course, but it was hinted that we need trig and also it takes care of both positive and negative very compactly: $cos~\frac{\pi}{3} = cos~\frac{-\pi}{3} = \frac{1}{2}$$\cos~\frac{\pi}{3} = \cos~\frac{-\pi}{3} = \frac{1}{2}$). It's likely to be symmetric in $x$ and $y$ so try out $cos~x + cos~y$$\cos~x + \cos~y$ for now. We've got the loop; now to check what that looks like when $h = 0$ so we can modify it for the square and woah we're already done.