It's been a while since anyone tried to raise $2 billion on the IPO market. But Zoetis is not your typical IPO. The company comprises the animal-health business of giant pharma Pfizer (PFE), which has been selling off some of its non-core divisions to make up for its lost blockbuster drugs. With more than $4 billion in annual sales, Zoetis is the global leader in its $22 billion industry. And the recent friendly receptions for the IPOs of Norwegian Cruise Line (NCLH)