Back in 2016, the Zimbabwean government passed Statutory Instrument 120 of 2016 also known as the Food Fortification Regulations. This instrument makes it compulsory for makers of various foodstuffs to including:

sugar
wheat flour
maize flour (mealie-meal)
edible vegetable oil and
salt

add important micro-nutrients to their products. Traditionally only salt has been fortified using iodine in a bid to compact conditions such as goitre. Now various minerals have to be added as they are deemed important. These include Vitamins A and D which are required to be added to maize for example as it will be a cheap, easy and effective way to combat malnutrition.

The Food Fortification Regulations of 2016 (SI 120 of 2016) states that all edible vegetable oil, wheat flour, maize flour, sugar and salt commercially produced or imported should be mandatorily fortified with micro-nutrients as prescibed in the relevant Zimbabwe food foritification standards.
This is a public health measure to prevent malnutrion due to micro-nutrient deficincies among the Zimbabwean population.
The notice from Ministry of Health threatening banning of unfortified products

The government has warned that they will soon ban those selling products that does not meet these requirements.