The only oneworld intercontinental routings into JNB/CPT are HKG-JNB (CX), LHR-JNB (BA), LHR-CPT (BA), MAD-JNB (IB) and SYD-JNB (QF). So pretty much, take your pick
If you want to fly South America-Africa then you need to fly SA/MH on the GRU-CPT-JNB-KUL route. If you want to do it the long way round, you could potentially fly SCL-SYD on LA and then SYD-JNB on QF.