Rachel Alexandra, the reigning champion at the Preakness, was 2009 Horse of the Year, while Zenyatta became the first female to win the Breeders' Cup Classic at Santa Anita Park last November.
Rachel Alexandra was undefeated in eight races in 2009 with earnings of more than $2.7 million.
Zenyatta is 14-0 and has earned more than $5.4 million.
She was 4 years old in 2008 when she won the Apple Blossom race.
"We have always pursued a goal of bringing the world's best racing to Arkansas," Cella said at a news conference. "That gives us the opportunity to fulfill the promises we continually make to our fans, our horsemen and all of our supporters."