Williams took out the NZ$1m Karaka Millions 2YO on La Dorada, and Shinn followed some 40 minutes later with a win in the NZ$1.5m Karaka Millions 3YO on Damask Rose.
Both wins were for New Zealand racing giant Te Akau, who booked both jockeys to ride key contenders in the two feature races.
Damask Rose started race favourite for Shinn in the 3YO, while La Dorada started second favourite for Williams in the 2YO.