Zverev had surgery to repair damaged ankle ligaments following an injury he sustained during his French Open semi-final against Rafa Nadal.
The German's return was further delayed in September after he suffered from a bone oedema, which forced him to withdraw from the Davis Cup Finals group stage. He then played in this month's Diriyah Tennis Cup exhibition event in Saudi Arabia.
Zverev, who rose to world number two in June and has since dropped to 12, said the injury was not a concern anymore but he will need more time to get his body up to speed after his tame defeat in the mixed-team tournament in Sydney.
"Physically, I'm not at the level I have to be. This isn't even a question. I'm getting tired a lot quicker than I always did," Zverev told reporters.
"I'm not as fast as I probably was. To be honest, I'm only pain-free for about two, three weeks now, since all Saudi Arabia basically. Before that, I had pain and I wasn't able to do all the different kind of things I want to do.
"I don't think it'll be a matter of tomorrow, after tomorrow. It'll be a few weeks until I'm back to the level I want to be."
Zverev's early promise is yet to yield a Grand Slam singles title and the 2020 US Open runner-up said he did not have high expectations ahead of the Australian Open starting January 16th.
"It's tough to set expectations high right now. It would be unrealistic and also quite stupid for me to set the expectations towards winning or something like that," Zverev, who reached the semi-finals at Melbourne Park two years ago, said.
"Of course, I want to win. Everybody wants to win. For me, it's about getting back the form that I'm used to."
