In pics: Day 2 highlights of Australian Open
Top-seeded Novak Djokovic and Simona Halep start this year's Grand Slam on a winning note. From Serena Williams' remarkable return to Zverev's unmatchable win, here are the major highlights from the Day 2 of Australian Open.
Novak Djokovic began his bid for a record seventh Australian Open title in easy fashion Tuesday, crushing 230th-ranked American Mitchell Krueger 6-3, 6-2, 6-2 on Rod Laver Arena.
The world number one had reached the Australian Open second round for 13 consecutive years and that streak was never threatened by the qualifier, who was making his debut at Melbourne Park.
Djokovic, appearing in his 300th Grand Slam match, did drop his second service game to go 1-2 behind in the first set but broke back immediately and went on to record his 259th match win in a major against a gritty but outclassed opponent.
World number one Simona Halep came from behind to defeat Kaia Kanepi of Estonia.
The Romanian was one set down and had to dig deep against Kanepi, who defeated her in last year's US Open first round, for a 6-7 (2/7), 6-4, 6-2 victory.
The 27-year-old was a finalist at Melbourne Park last year and will be looking for a major improvement to go deep in this year's tournament after such a shaky start.
Serena Williams made a return to the Australian Open court with a win as the American tennis star defeated Tatjana Maria in straight sets 6-0, 6-2 to move into the second round.
While the German, Maria, had no answers to Williams' powerful game for most parts of the match.
Germany's Alexander Zverev overpowered Aljaz Bedene to win their first-round match 6-4, 6-1, 6-4 at the Australian Open.
Zverev, who is considered a title contender, went down a break midway through the first set, which seemed to prod him into action.
He won the next eight games and Bedene never recovered.
The seven-time Grand Slam champion Venus Williams of the US celebrated her victory against Romania's Mihaela Buzarnescu during their women's singles match.
She dropped the first set in a tiebreaker 7-6(3) but won the other two.
The score was 6-7 (3/7), 7-6 (7/3), 6-2.
Japan's Naomi Osaka clubbed her way into the second round by beating Poland's Magda Linette 6-4, 6-2.
It was Osaka's first Grand Slam match since her breakthrough US Open triumph last year, which was partly overshadowed by a row between her final opponent Serena Williams and umpire Carlos Ramos.
Osaka's heavy ball striking makes it very difficult for opponents to trade blows with her.
"For me, I'm aware of people saying anyone in the top 10 can be No. 1 right now - but for me, that's not really my goal," Osaka, the fourth seed, told reporters.
Seventh-seeded Karolina Pliskova defeated Karolina Muchova 6-3, 6-2 to reach the second round.
The 26-year-old took just 69 minutes to defeat her compatriot.
"It's a good start, I'm happy I didn't have to spend too much time on the court. I don't know why but I always play good tennis here (in Australia)," she said after winning the match.
An injury-hampered Nick Kyrgios crashed out of the Australian Open first round with a 6-4, 7-6(5), 6-4 thrashing at the hands of Milos Raonic that capped a dismal day for the host nation.
A prodigious yet polarising talent, former quarter-finalist Kyrgios suffered his earliest exit from Melbourne Park, leaving further doubts as to whether the 23-year-old Australian can realise his potential.
In a match neatly summarising Kyrgios's roller-coaster career, the 52nd-ranked player spent much of the night muttering expletives about the condition of his right knee and had a trainer working on the injury between sets.
France's six-time singles' title winner Alize Cornet wins a 6-2, 6-2 over Spain's Lara Arruabarrena-Vecino during their first round women's singles match on day two.
Ukraine's Dayana Yastremska hits a win against Australia's Samantha Stosur with 7-5, 6-2 during their women's singles.