Features the Maned Wolf and the walkthrough exhibit for butterflies.
Adds the Amur leopard and incredible "backstage" scenery.
Cracked games often suffer from crashes and bugs that were fixed in official patches, but because your version isn't linked to a real launcher, you won't receive those updates. How to Get Planet Zoo DLCs for Cheap (Legally)
Planet Zoo is a frequent guest on Humble Bundle. You can sometimes get the base game and several DLCs for under $15, with a portion of your money going to charity.
These sites often sell official Steam keys at a significant discount. Just ensure you are buying a key for your specific region. Which DLCs Should You Prioritize?