It must be love. When I saw Zim actually sharing his food with Gem out of his own dish, I was stunned. Now I know there's a stall partition separating them. But he's very hoggish about food, and he's taken his food bowl away from me plenty of times as I've been filling it so I know he could have easily done so with Gem. At the very least I expected him to nip at her or toss his head. But instead he so sweetly shared his meal with her.
This is like the spaghetti scene in "Lady and the Tramp" or perhaps like two teenagers with two bendy straws and one glass at the soda counter. It made me go "Awww!"