The defending champion opened confidently with a rock-solid service game to love, and the Russian's nerves will have settled after leveling at 1-1 in front of a packed Center Court crowd on a warm, overcast day at the All England Club.
Zvonareva took the American top seed to deuce in game three before Serena clinched it with a third ace.
The first signs of pressure on the 21st seed came in the sixth game when three forehand errors gave Williams the first break point of the match.
But Zvonareva hit a pinpoint forehand into the corner to fend that off, and then a netted return from Williams made it 3-3.
The decisive breakthrough came in game eight when a double fault from Zvonareva took the game to deuce before a long backhand from the Russian gave Williams another break point.
The American smacked her racket into the ground in frustration when she netted a backhand return but a superb lob after a lucky netcord gave Williams another break point.
After lashing a winning forehand down the line, she celebrated with a fist pump and on bended knee.
Zvonareva earned her first break point of the match in game nine but Williams clung on and a long forehand gave Serena the first set after 36 minutes.
(Editing by Miles Evans)
