Zardes goals lift Galaxy, Gerrard exits injured
San Jose were down a man for all of the second half after Simon Dawkins was shown a red card in first-half injury time for a tackle on Sebastian Lletget.
The Galaxy took advantage, with Zardes opening the scoring in the 56th minute.
He scored his second six minutes later, pouncing on Earthquakes defender Kip Colvey's weak clearance to beat San Jose keeper David Bingham.
San Jose pulled one back through Chris Wondolowski in the 89th minute.
But Victor Bernardez tripped Robbie Keane in the penalty box moments later and Keane connected from the spot for the final goal.
Galaxy midfielder Steven Gerrard's night was cut short when the was forced off in the opening minutes with an apparent calf injury.
The former England international was attempting to track down a cleared ball when he pulled up, and he departed after an examination by medical staff.
In other matches, FC Dallas spoiled the 2016 season debut of Montreal's star striker Didier Drogba with a 2-0 home win.
Drogba, the former Ivory Coast and Chelsea star, sat out the first two matches of the season with knee trouble.
Both of Dallas' goals came late in the second half and courtesy of a pair of Argentines -- Mauro Diaz and Maximiliano Urruti.
Impact head coach Mauro Biello sent Drogba in the 70th minute in a bid to break a scoreless deadlock.
Instead, Diaz scored in the 79th and Urruti added another in the 87th.
Felipe struck twice late in the second half to lift the New York Red Bulls to their first win of the season: a wild 4-3 home victory over the Houston Dynamo.
The midfielder scored on two long range efforts, including a dramatic curling free kick, to help the Red Bulls rally after falling behind 2-1 and 3-2.
Will Bruin scored twice for Houston.
The Portland Timbers battled back late against Real Salt Lake, with Fanendo Adi scoring in the 79th and converting a penalty in the 84th in a 2-2 draw against a Real Salt Lake team reduced to nine men.
Salt Lake had seized control with a goal from Joao Plata in the 16th.
They were already down one man after the sending off of Kyle Beckerman when Yura Movsisyan made it 2-0 in the 58th minute, and Salt Lake were further reduced when Jamison Olave was sent off in the 83rd.
In Chicago, the Fire played to a scoreless draw with the Columbus Crew and the Vancouver Whitecaps defeated the Sounders in Seattle 2-1 with two penalties converted by Pedro Morales.