I know you can apply a displacement, though can you render a low poly model with a normal map in zbrush?
It is not currently possible to render your normal maps within ZBrush. Normal maps are hardware rendered, while ZBrush is software rendered. So to view normal maps on the model you need to load the model into a program that uses hardware rendering.
That being said, normal map rendering is highly dependent upon the engine that’s running it. What looks good in one engine can be awful in another. For that reason you are better off using GoZ to send your model to your other application. You can then preview the normal map there, using the engine that will be used for the final render.