What prevents the Congo and zambezi rivers from being more useful for trade and transportation?

The Congo and Zambezi rivers face significant challenges for trade and transportation due to their turbulent waters, rapids, and waterfalls, which hinder navigation. Additionally, seasonal flooding and variable water levels can make parts of these rivers impassable. Limited infrastructure, such as inadequate ports and roads, further restricts access and efficient transport along these waterways. Lastly, political instability and economic challenges in the surrounding regions can impede investment in necessary improvements.