Zanotti has yet to win on the European Tour and lost his card at the end of last season after finishing 140th on The Race to Dubai, only to swiftly regain it by coming second at the Qualifying School.
The 30 year old also returned a second round of 66 and, like Santos, has not dropped a shot in 36 holes. Playing partner Simon Wakefield added a 67 to his opening 66 to lie five shots off the lead on nine under.
South African players have won nine of the last 12 European Tour events on home soil and Jean Hugo, Ulrich van den Berg and Ruan de Smidt were all a further shot back on eight under after rounds of 66, 68 and 66 respectively.
As the afternoon session progressed American Qualifying School graduate John Hahn joined Santos on 14 under with a sensational scoring burst over his back nine.
Having started at the ninth and turned two under par, Hahn had four birdies and an eagle three at the third over his next five holes to be eight under for his round with four holes remaining.