Williams wins 6-2, 6-2 to give her team a 3-1 lead in the best-of-five gold group final.
It followed a hard-fought 3-6, 6-4, 6-4 win for Gisela Dulko over Anna Chakvetadze after the Americas and Russia were tied at 1-1 overnight.
Williams, who struck 10 winners and six aces, looks in great shape for this month's Australian Open, which she has never won.
Earlier in the tournament she crashed world number one Jelena Jankovic by the same scoreline.
"I've been here so many years and this is the perfect way for me to prepare for the Australian Open," Williams said after her team's win.In the final match of the exhibition tournament, Williams and Coco Vandeweghe beat Chakvetadze and Alexandra Panova 6-4, 6-1 in doubles to seal a 4-1 victory for the Americas.
Referring to her victories over Jankovic and Zvonareva, Williams said: "(They are) very accomplished players and experienced and both of them played great last year so it's definitely a great way to start the year with wins against such talented players."
On Friday, Williams beat Chakvetadze 7-6 (7/1), 6-3 to give the Americas the lead but Russia hit back through Zvonareva, who beat Dulko 6-4, 0-6, 6-3.
Asia-Pacific won the silver group final 3-0 against Europe.
(Via AFP; Images via Yahoo! Sport)