In mobutu sese seko’s final years of rule, zaire was largely reduced to a economy.

The answer is: Barter

Barter economy refers to an economic system  which does not possess a universal medium of exchange (i.e : Currency).

In barter economy, everytime people want to obtain a product that they need, those people need to trade the needed product with other products that they already owned. (for example, if person A who is a chicken farmer want to obtain milk from person B, person A can trade the eggs that he produce for the milk that person B produce)