Before you call PETA, let me just say that Mattie is clearly the instigator here. She grabs Zoe's legs and bites them, or wraps all four legs around Zoe's head/muzzle/ears and boxes/kicks/bites until a frisky poodle just can't stand it any more, and gives chase.
Then Zoe pounces frighteningly near Mattie, and Mattie shoots up in the air with all her paws out, twists around in mid air, and dashes behind a chair. If Zoe lies down for a minute, Mattie races out from behind something and leaps through the air at Zoe, pouncing right in front of her nose, and dashing off. Or she rolls over right under Zoe's nose and grabs her muzzle...see above. Or she chews on Zoe's paw to wake her up. They can go on like this for well over an hour, twice a day.