The duo, both 34, sustained injuries last season in the A-League Men, with Kruse (knee, Melbourne Victory) and Zullo (calf, Sydney FC) now up for grabs after being released by their former clubs.
"They are both here training with us and both coming back from fairly serious injuries and looking to rehabilitate themselves," Moon told reporters on Wednesday.
"They are both Queenslanders … and they want to tick boxes in their own minds knowing they can overcome what they've had over the last couple of years and see if they are ready to play again.
"If that time comes I'm sure not just us but other clubs would look at (signing them).
"First and foremost, we are accommodating two former players at the club and two former Socceroos.
"They both have much to offer the game and they are both great human beings."
Asked whether the Roar could afford to sign the players, Moon said: "That is a club decision but for what they could add to this club I certainly would endorse them."
The presence of the pair has already been a boost to the winless Roar ahead of their away clash with Western Sydney on Saturday.
Defender Joe Knowles idolised Kruse, who has 75 Socceroos caps and carved out a successful career in Germany between his A-League stints, as a youth.
"As a winger I look up to Krusey," Knowles said.
"Any little piece of advice you can take from someone like that is only going to help you.
"Growing up in Australia you watch the Socceroos and to see somebody like Robbie make that many appearances and play overseas, to be training with him is mind blowing.
"Hopefully he can get his body right and we can see him in the Brisbane Roar colours."
