When Tania Santana and her brother Paulo Oliveira opened Circus over ten years ago, they gave the stodgy lower-Sixties stretch of Lexington Avenue a transfusion of Brazilian cuisine and potent caipirinhas. But when the ground floor of the old Peter Kump cooking school three blocks from Santana's Yorkville apartment became available, she jumped at the chance to colonize her own neighborhood with the more casual, lower-priced Zebú Grill. Named for a Brazilian breed of humped cattle and outfitted with rustic wood tables, the homey restaurant offers Brazilian standards like fried yuca, empanadas, and a churrasco, a protein-packed mixed grill for two.