The world number eight, playing in his first tournament since the Miami Open, sent down 19 aces and won 93% of points on his first serve.
Up next for the towering South African, who reached last year's Wimbledon final, is Gilles Simon or another local hope in qualifier James Ward.
Murray's Olympic love affair ends with doubles defeat
Daniil Medvedev, seeded fourth, powered past Spanish veteran Fernando Verdasco 6-2 6-4 to move into the next round where he was joined by Marin Cilic who staved off a late comeback attempt by Cristian Garin to prevail 6-1 7-6(5).
French qualifier Nicholas Mahut overcame American Frances Tiafoe 6-3 7-6(5) while Diego Schwartzman of Argentina beat Alexander Bublik 6-2 6-3 to set up a meeting with Cilic.
Murray and Salisbury pull off major upset at Olympics
Wimbledon order of play, day four - Federer, Barty, Medvedev in action