For an evaluation of a South African higher education diploma, we check 2 things:

Recognition of the higher education institution

On the website of the Department of Higher Education and Training (DHET) you can find overviews of recognised higher education institutions:

Accreditation of the study programme

You only have to check the accreditation of the study programmes for diplomas from private higher education institutions. The overview of recognised private higher education institutions from the DHET includes the accredited study programmes per institition.