Mislav Orsic and Erling Haaland scored hat-tricks on their Champions League debuts, marking the first time two players have done so in the same edition of the competition.
Croatian attacker Orsic, 26, notched his treble in Dinamo Zagreb's 4-0 home win over Atalanta on Wednesday.
The result put Dinamo top of Group C, which also contains Shakhtar Donetsk and Manchester City.
Orsic's exploits followed 19-year-old Salzburg striker Haaland netting three times in a 6-2 victory over Belgian side Genk on Tuesday.
Salzburg are top of Group E ahead of Napoli and Liverpool.