"He hasn't retired. He is still in our plans, but it is important in terms of succession plans that we look at other options," Sport24 quoted Zondi as saying.
Current Test and T20I captain Du Plessis was not named in the 15-man squad for the upcoming three-match ODI series and the team's captaincy was handed over to wicketkeeper-batsman Quinton de Kock.
Zondi further said that the exclusion of Du Plessis and Kagiso Rabada is part of workload management, keeping in mind the ICC T20I World Cup later this year.
"It is the same for KG (Rabada). It is about managing workloads and this is an important year for us in T20 cricket with the World Cup coming up towards the end of the year (in Australia in September). It's just about giving opportunities to other guys," Zondi said.
"Anrich was going to be one of our key bowlers at the World Cup before he got injured and he has been bowling a lot in the Test series, so there is no way that we are throwing him or anyone else away," he added.
When asked further about Du Plessis' future and if he has any plans to retire, Zondi said they would continue to factor Du Plessis into their plans until he said they shouldn't.
"At the moment he hasn't said anything to me," he said.