For a book that takes place in Washington, there sure is a lot of talk about zebras. It's not even like this book takes place in a zoo.
The first time we see the striped menace is when Enzo is home alone after Eve and Zoë have run off without him. We can't tell if Enzo is having a hallucination, or if this zebra has magically come to life to destroy everything in Zoë's room. In fact, it's something we're that unclear to us to this day. Either way, Denny, Eve, and Zoë come home to find the toys destroyed, with Enzo crying zebra.
The zebra comes back, though, again and again. Once, it appears in Zoë's room in her grandparents' house. Later, it appears in the pen that Mike hands Denny when he's preparing the sign the settlement papers. It's then that Enzo realizes that the zebra isn't a real animal that parades around and destroys people's lives: it's actually a metaphor for our own demons, the wickedness that plagues us and causes us to act on our baser instincts.
So…the zebra isn't real? Does that mean Enzo ripped up the toys, or not?
When he thinks of the zebra dancing near Eve, Enzo's really talking about her fear of death, and the fear of the malignant thing inside her brain that's trying to destroy her. When he sees the zebra in Mike's pen, he realizes that Denny wouldn't be signing those settlement papers if he were using his best judgment; it just that he's been so beaten down by Maxwell and Trish that he's at his wits' end.
As Enzo says, "I suddenly realized. The zebra. It is not something outside of us. The zebra is inside of us. Our fears. Our own self-destructive natures. The zebra is the worst part of us when we are face-to-face with our own worst times. The demon is us!" (49.27)
This probably means that Enzo really did demolish Zoë's stuffed animals that fateful night, but he was probably suffering from extreme hunger, so we have to forgive him. Besides, he was totally contrite when he asked for Zoë's forgiveness, and that counts.
That also means we can definitely blame the zebra the next time we accidentally stay up too late watching Netflix or forget to wash the dishes.