After Aleksandar Vukic and James Duckworth suffered first-round defeats, compatriot Hijikata was eliminated in round two, 6-4 7-6 (7-0), in just 88 minutes.
The sixth-seeded Czech broke in the seventh game of the opening set, before taking it out after holding serve two more times.
Hijikata, the world No.73 from Sydney, broke for 2-0 in the second set but immediately relinquished his advantage in the third game.
Machac was broken again when serving for the match at 5-4, but swept through the tiebreaker to set up a quarter-final clash with Canadian Denis Shapovalov, a late night 2-6 6-3 7-6 (7-2) winner over top seed Taylor Fritz.
Elsewhere on Friday (AEDT), third seed Tommy Paul and fellow American Reilly Opelka were victorious, but compatriots Ben Shelton, Frances Tiafoe and Michael Mmoh were knocked out.
Defending champion Paul downed close friend Ethan Quinn 6-4 5-7 6-4, after failing to serve it out in the second set.
"I've been in these situations a little bit more," 27-year-old Paul said when addressing the difference maker in the match.
"I felt a little more comfortable probably. That's how you win the big matches, being better in the big moments. I tried to do that today. It would've been nice to serve out the second set, but do it in three."
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