I do not know the specifics of labor law in Zimbabwe. However, by following normal logic, you don't seem to have a strong case. You have resigned. The resignation stands as it is. Your employer suspended you and then terminated you. Since you had already resigned, instead of terminating (having realized that termination will be a complex process), he accepted your resignation. He has the right to do that. And if he is giving you a clear relieving letter, you will have little to complain about.
However, I don't think the whole story is being told. You resigned, and your employer persuaded you to stay on. So obviously, he needed/wanted your skill set. So what happened in 5 days that he wanted to get rid of you as soon as possible? You wanted to leave. You stayed for 5 days extra. So now, how does this really affect your plans? You can proceed with whatever is the reason why you resigned, right?