Pandza, a Bosnian international, and former Hearts man Zaliukas are available on free transfers, but McCoist does not believe that they have the funds to accommodate both players.
The 50-year-old told the club's official website: "I've made it clear that we'd love to bring in a centre-half and Marius has done really, really well.
"Himself and Boris are two players that we've been looking at and I'm very keen to strengthen that department.
"I'm not sure if there's a budget for both and I would need to speak to chief executive Craig Mather about that."
Rangers have began the season in superb fashion, scoring 18 goals in registering 12 points in their opening four games.