NEW YORK – If Zenyatta wins the Breeders’ Cup Classic on Saturday, finishing her career 20 for 20 with a victory over the best horses she has ever faced at the iconic American showcase of 10 furlongs on the dirt at Churchill Downs, it will be a spectacular moment in all of racing history. It would of course also rightly make her a virtually unanimous choice as the nation’s Horse of the Year, an honor for which she finished second in the balloting in 2008 and 2009.