The agent told me that I could route the trip to South Africa via Argentina one way and Europe the other way. And, yes if you arrive in EZE and have to wait three days for the next MH flight - that doesn't count as a stopover. She also told me only one stopover is allowed. So one could fly from the USA to EZE, spend two nights there waiting for the MH flight, fly on to South Africa, spending as long as you want there, and then fly back to the USA via Europe, spending as much time as you want there using your one stopover. Due to the one stopover only rule, I don't think this will work in the other direction as Delta/Copa have daily flights from EZE to the USA.