Can I still use my South Africa passport to travel to South Africa after becoming a New Zealand citizen?

I was born in South Africa then migrated to New Zealand. Before I obtained my NZ citizenship, we had to renew my South African Passport. At the moment I have a valid NZ passport (expires end of this year) and a valid S.A passport (expires in 5 years).

I was over 18 years old when we applied for NZ citizenship and did not send any additional paperwork in to hold on to my S.A citizenship. So I don't have Dual-citizenship.

My S.A passport still has my NZ Permanent Residency paperwork in it which we needed to obtain NZ citizenship.

With this new Visa Requirements that came in force, it's going to take too long to get a Visa on my NZ passport to enter S.A. We have a family emergency and need to fly out ASAP.

Can I still use my S.A. passport to travel to S.A and back to NZ even though I have not retained my citizenship in S.A? Or would I get into trouble at the border for using my S.A passport while not having citizenship there? Or even worse denied entry to NZ because I did not use my NZ passport to come back into the country?