"Both horses are absolutely thriving and have improved," Neville Parnham said.
Parnham will saddle up Zipaway in the Group 1 Australian Guineas (1600m) and Bustler in the Group 2 Blamey Stakes (1600m) at Flemington.
Zipaway is an outsider in the Australian Guineas, but Parnham, a WA Racing Hall Of Fame member, will not be surprised if he caused an upset.
Parnham has never hidden his admiration for Zipaway, a horse he bred and believes the son of Playing God has the capacity to reach the elite level.
Zipaway gave a glimpse of his potential on home soil last year when he took out the Group 2 WA Guineas (1600m) at Ascot in thrilling fashion.
He then further enhanced his growing status when finishing third behind Dom To Shoot and Zaaki in the Group 1 Northerly Stakes (1800m).