Well he can only eat 食 that has コーン, トウモロコシ starch I think but for now Zim can only eat ワッフル but later he might get sick.But he might not if they aren't made によって Gir.Who knows what he put in them.
ZIM HATES ALL EARTH 食 THEY CAUSE HIM PAIN!!! for example beans make him ooze green slime and make his head all big, water(i think that counts as a food) feels like acid to irken people, BUT HE LIKES ワッフル TO SOME EXTENT