The Pole and the Monacan defeated Frenchmen Jérémy Chardy and Fabrice Martin 6-3, 5-7, 6-2 in the semifinals of the Grand Slam event at Melbourne Park on Thursday.
Zieliński and Nys will face home favourites Jason Kubler and Rinky Hijikata in the championship match on Saturday.
Meanwhile, Poland's Magda Linette was on Thursday set to play Belarusian Aryna Sabalenka for a place in the final of the women's singles at the Australian Open.
Linette is the last Pole standing in the singles at this year's Australian Open, which runs until Sunday.
Poland's world No. 1 Iga Świątek has crashed out of the tournament, after being eliminated by Elena Rybakina of Kazakhstan in the fourth round of the women's singles.
On the men's side, Poland’s Hubert Hurkacz bowed out of the tournament after being beaten by American Sebastian Korda in the fourth round of the singles in Melbourne.
Source: IAR, PAP