Australia moved within reach of victory within two days in the first test against South Africa as the Proteas' batsmen crumbled on a menacing Gabba wicket on Sunday.South Africa were 66 for seven at tea, with the scores level, after the home side's bowlers took five wickets in the middle session.South Africa number five Khaya Zondo was 14 not out, with tail-ender Kagiso Rabada on one, the pair left with a 'mission impossible' to set Australia's batsmen a total to chase.The Proteas resumed on three for two after lunch and added only two runs before Sarel Erwee fell for three with an edge off Pat Cummins that Cameron Green leapt high to catch at gully.Temba Bavuma and Zondo combined for a 42-run partnership but Nathan Lyon broke it by removing Bavuma lbw for 29.The Proteas promptly collapsed, losing 4-17 as Scott Boland dismissed Kyle Verreynne and all-rounder Marco Jansen for ducks in three balls.Keshav Maharaj lingered for a bit longer before he was caught behind for 16 by Mitchell Starc, who earlier claimed his 300th wicket by bowling number three Rassie van der Dussen for a duck with a trademark in-swinging yorker.Earlier, Rabada (4-76) and Jansen (3-32) had done well to restrict Australia, with the latter denying Travis Head (92) a century after the home side resumed in the morning on 145 for five.Head and all-rounder Cameron Green were cruising until Jansen had Green out for 18, with Erwee scrambling from first slip to catch an edge that pinged off Keshav Maharaj's hands.Jansen then had Head caught down the leg-side eight runs short of his century before Lungi Ngidi and Rabada cleaned up the Australian tail.