[SideburnsOfDoom]

"SA" is ambiguous. People do use to to refer to "South Australia" (the state) or also "Saudi Arabia" ISO 3166-2 country code.

ZA is not ambiguous, it has that going for it.

[botanical]

True, but I meant in South Africa, SA is the most used. Less so with RSA or ZAR. ZA is somewhat used but SA (I would say) dominates in conversation and in written text.