Their eight-under efforts in sunny, still conditions gave them a one-shot lead from Ireland’s Paul McGinley, and English pair Danny Willett and Chris Wood.
Australia’s Fraser managed five birdies in the last six holes of his morning session, while Paraguayan Zanotti's afternoon round boasted two eagles, seven birdies, a bogey and a double bogey.
Wood, meanwhile, revealed that he led an unorthodox charge on foot through nearby country fields after he and several other players were caught in bad traffic before the event.
"We finally decided to leg it when we had gone one kilometre in 20 minutes - it was that bad," Wood said.
"It was about 3.5 kilometres and I was a bit sweaty when I got here, but it was worth it."