Ryan Rickelton and Tristan Stubbs have been called up as replacements for De Zorzi (hamstring) and Ferreira (clavicle fracture), after their original omission from the squad had raised plenty of eyebrows when it was announced.
Miller has an adductor muscle injury and is ruled out of the three-match T20 home series against West Indies that starts on Tuesday, but could yet recover in time for the World Cup.
Rubin Hermann, who has been in excellent form in the ongoing SA20 tournament, will replace Miller in the squad for the West Indies series.
South Africa open their World Cup campaign against Canada in Ahmedabad on February 9, and also play Afghanistan, New Zealand and the United Arab Emirates in their pool.
Updated South Africa T20 World Cup squad:
Aiden Markram (captain), Corbin Bosch, Dewald Brevis, Quinton de Kock, Marco Jansen, George Linde, Keshav Maharaj, Kwena Maphaka, David Miller*, Lungi Ngidi, Anrich Nortje, Kagiso Rabada, Ryan Rickelton, Jason Smith, Tristan Stubbs
*Subject to fitness test