Lacko advanced to Sunday's final with a 7-5, 7-6 (7-3) win over sixth-seeded Marcos Baghdatis of Cyprus. It will be Lacko's first career ATP final.
Youzhny, meanwhile, grabbed the other finals slot with a 6-3, 6-4 win over Germany's Michael Berrer.
Berrer was denied in his bid to make a second straight finals appearance at the Zagreb event.
Russia's Youzhny, meanwhile, earned his 18th career final and will be seeking his eighth title.