The two defeated the Austrian pairing of Alexander Erler and Lucas Miedler 6-3, 2-6, 13-11 in the quarterfinals on Thursday.
The 27-year-old Polish player and his 33-year-old doubles partner will now face Finland's Harri Heliovaara and Australia's John Peers for a place in the championship match at the outdoor hard-court tournament in Mexico.
Zieliński and Nys in November defended their doubles title at the Moselle Open tennis tournament in the French city of Metz.
The 2024 Mexican Open runs until Saturday.
(gs)
Source: IAR, PAP