The paceman bowled with typical skill and fire to claim his 26th five-wicket haul in the final innings as the hosts won the second test by 204 runs to take the two-match series 1-0.
Groin injuries have been hampering Steyn and a serious shoulder problem meant he missed the series against England in December and January.
But the devastation he caused against the Kiwis, taking two wickets in the first over of their second innings, put South Africa on the right road.
With a series coming up in Australia in November, his return, and that of new-ball partner Vernon Philander, offers the potential of a close contest.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"Test matches are tough, the cricket is really, really difficult," Steyn told reporters after helping to bowl New Zealand out for 195. "I don't think I'm in a position to say 'I'm back'.
"I need a couple more test matches, more game time, just to learn how to start playing the game again. I'm getting there and there has been reward but I'm nowhere near what I'm capable of."
Philander suffered a serious ankle injury playing a warm-up game of football in India in November and also made his comeback against the Kiwis.
"Vernon is a phenomenal bowler. That was probably something we lacked against England because Vernon is the kind of bowler who doesn't give you anything," said Steyn.
"To be able to bowl with him makes me feel free, I can run in and do what I want to do. You know that at the other end he is going to tick over at two runs per over.
"You can feel safe and he can still knock guys over. He is so skilled."
Steyn's haul on Tuesday took him to 416 test wickets, past Pakistan's Wasim Akram on the all-time list, and there were no physical side effects.
"The more I bowl, the quicker I'll bowl and the more confidence I'll have to use my whole body again," he said.
"If you get wickets ... there is nothing to complain about."
(Editing by Tony Jimenez; mark.gleeson@thomsonreuters.com; +27828257807; Reuters Messaging: Reuters Messaging: mark.gleeson.thomsonreuters.com@reuters.net)
