Two-time champion Mats Wilander of Sweden moved into the fourth round of the $1.5 million Australian Open tennis championships at Kooyong yesterday. The third-seeded Wilander, bidding to win the event for the third straight year, romped to a 6-2, 6-3, 6-2 triumph over unseeded Leif Shiras of the United States.

Ivan Lendl of Czechoslovakia, the top seed, defeated American Ben Testerman, 6-3, 1-6, 6-3, 6-2, but complained of being unable to keep his footing on the grass courts. He also was fined $500 for uttering an obscenity. Second-seeded American John McEnroe was sluggish in defeating Nduka Odizor of Nigeria, 4-6, 6-2, 6-4, 6-2. Odizor provided the crowd with laughs by once acing McEnroe with a soft underhanded serve when the American was playing deep for the return.

Defending champion Chris Evert Lloyd and second-seeded Martina Navratilova both eased into the women's quarterfinals, but Catarina Lindqvist of Sweden, seeded 10th, rallied from a set and a break down to upset fourth-seeded Pam Shriver of the United States, a grass court expert, 3-6, 6-3, 6-2.

Tom Wilkison of the United States and South African Christo Steyn pulled off the biggest upsets in the men's third-round singles. Steyn surprised 10th-seeded Brad Gilbert of the United States, 2-6, 6-4, 6-4, 7-5, while Wilkison ousted his 12th-seeded compatriot Paul Annacone, 7-5, 6-3, 6-3. Annacone also was fined $500, for racket abuse.

Wilander agreed with complaints by McEnroe and Lendl that the courts are too slippery, but said: "I don't think it's any worse than last year."

"I'm trying to accept things philosophically," said Lendl. "If I don't win here, then I'll start my holidays a few days earlier." Lendl, asked what could be done to improve the courts, said: "I think they should pour concrete on it overnight and start again tomorrow."