The Zoo Crimes Division is a part of The City's police force, dedicated to, as the name suggests, dealing with zoo-related crimes. They first appear in Issue 19 of the Invader Zim comic series.
Summary[]
Due to the attempts by the Roboparents to prove that they have jobs like normal people, Zim is forced to create a zoo in the front yard of his base, full of animals created from bio-slurry. These bizarre and misshapen animals disappoint and disgust the Skoolchildren, who accuse the Roboparents of being grifters.
Dib then goes to the police and, when they refuse to listen to his claims about Zim being an alien, tells them about the grifter rumor, causing them to call in the ZCD. A squad, led by Immola Krom, descends on Zim's base.
A quick inspection leads them to determine that all the animals are in fact fake, so Krom gives the Roboparents one day to get real ones or face the consequences, so in an attempt to fix the situation, Zim and GIR break into the Town Zoo, which the ZCD protects, and steals a bunch of animals, only to toss them out of the Voot Runner when he grows disgusted by their stink. So instead of using them to replace the fake animals in his zoo, he simply spruces them up to try and pass the inspection.
However, Krom is not tricked, and she places the Roboparents under arrest. But despite Dib's hopes and Zim's fears, she doesn't arrest Zim as well, seeing him as just an innocent child caught up in his parents' crimes. So, the ZCD leaves him alone and just carts the Roboparents off to jail.