You know how Dib sits on his roof listening for aliens and whatnot? I would imagine Zim acts the same, but he's eagerly waiting for his Tallests to call even though they've eliminated all possible ways of contacting Zim. As much as I love those two nutballs, they can be total jerks.
It's alright, Zim. You'll find someone soon you can depend on.

The moon has been so bright a full lately.

Zim © Jhonen Vasquez
Art by  twiggihighwind