Mighty victories for veteran James Duckworth and never-say-die Dane Sweeny on day three also guaranteed the bumper Australian contingent its equal-most successful opening to the Melbourne Park major this century.
But Preston's life-changing 6-3 2-6 6-3 victory over Zhang Shuai and Inglis's epic, three-hour, past-midnight 7-6 (8-6) 6-7 (9-11) 6-4 win over compatriot Kim Birrell ensured six Australian females will feature in the second round of the Open for the first time since 1992.
Back then, before the Australian Open became the behemoth event it is nowadays, retired doubles great Rennae Stubbs and incumbent Billie-Jean King Cup captain Nicole Pratt led a fleet of eight Australian women into the second round.
With the progression of Preston and Inglis, along with Storm Hunter, Talia Gibson, Ajla Tomljanovic and Priscilla Hon, Australian women's tennis is suddenly replicating the good old days.
After dropping down levels to gain valuable match practice, Preston secured a career-changing pay day of at least $225,000 with her breakthrough maiden grand slam win.
Fresh from a breakout run to the semi-finals at last week's Hobart International, Preston held her nerve to down Chinese veteran Zhang in one hour and 33 minutes.
Sweeny then completed a similarly significant first ever-win at a major, a memorable 6-7 (3-7) 7-5 6-4 7-5 victory over retiring French veteran Gael Monfils, to continue Australia's excellent start to the year's first grand slam.
Like Preston, Sweeny is guaranteed a cheque for almost a quarter of a million dollars for progressing to the second round.
Contesting his 17th Open, and 13th in the main draw, 33-year-old Duckworth conjured a mighty comeback to down qualifying lucky loser Dino Prismic 7-6 (7-4) 3-6 1-6 7-5 6-3 in four hours and 12 minutes to ensure Australia have 11 players in the second round singles.
That is the equal-most since 1992.
Duckworth's reward is a show-court showdown with two-time defending champion and world No.2 Jannik Sinner on Thursday.
While Duckworth has been there and done that, Preston is savouring her finest run yet at a slam, let alone her home major.
Just two weeks ago in qualifying for the Brisbane international, Zhang had beaten the 20-year-old in three sets.
But swinging freely from both wings, the West Australian was able to turn the tables on the big stage.
Her victory came after Preston took the bold step back to play ITF 35s, out of the spotlight, so she could play regularly.
"I dropped down a couple levels just to get my match count up, because I wasn't playing a lot, and that really helped," Preston said.
"I had a really good pre-season in Brisbane ... then last week in Hobart to be able to get a couple of really good wins under my belt really helped with my confidence leading into this week."
The only Chinese player with more match victories at Melbourne Park than Zhang is retired 2014 champion Li Na.
"It makes it more special having done it here at home in Australia," said Preston, who will next play Czech No.13 seed Linda Noskova.
"The first win at any grand slam is special; it takes a lot of hard work, and I've been working really, really hard."
While Preston was all smiles after her win, the news was nowhere near as good for Australia's top-two-ranked women's stars.
Teenage 30th seed Maya Joint bowed out 6-4 6-4 against Czech Tereza Valentova, while former top-10 mainstay Daria Kasatkina blew a third-set service break in a deflating 6-7 (7-9) 0-6 6-3 loss to Czech qualifier Nikola Bartunkova..
Australian wildcard Chris O'Connell is also out after enduring a heart-breaking 4-6 7-6 (9-7) 6-7 (3-7) 6-2 6-3 loss to American qualifier Nishesh Basavareddy.
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