Zulu, who joined Sundowns in January from the now-defunct Platinum Stars, is yet to play this season as Tebogo Langerman and new signing Lyle Lakay are ahead of him in the pecking order at Chloorkop.
The Orlando Pirates academy graduate recently revealed there was interest in his services in the previous transfer window, but Downs coach Pitso Mosimane was unwilling to let him go.
When Zulu was playing regularly for Stars he was called up by former Bafana coach Ephraim Mashaba for a 2017 AFCON qualifier with Mauritania and a friendly with Senegal.
However, the 25-year-old had an international debut to forget, as he was sent off in a 3-1 loss to Mauritania at the Olympique de Nouakchott in 2015.
Zulu feels he has learnt from that experience and improved as a player.
"I got calls from other coaches and they told me that it's part of growth, you have to build on this. That is when I started building up.
"After that game I've become a better player. Now I'm at a better club and any day, any time the call can come."
He adds: "Another thing, when you play for bigger teams it is easy to go overseas. It is easy to get a job when you have left a bigger team, and it's also easy to get another job from other teams."