Adding layers only automatically occurs while you are working directly in the Desktop environment, which includes the Python Window. In script tools you explicitly have to add layers to a map. Look at arcpy.mapping.AddLayer, arcpy.mapping.InsertLayer, and arcpy.mapping.Layer to deal with the map TOC. Once the TOC is handled the zoom function should work. If you are just selecting one point you may want to look at panToExtent. Assuming you have a Layer called lyr with a selection this will pan the dataframe:
df.panToExtent(lyr.getSelectedExtent())
Edit: MakeFeatureLayer_management is only for the geoprocessor and converts a feature class on disk to a layer in memory that the geoprocessor can use. Models and scripts use this tool frequently to make feature class outputs into layers so that other geoprocesses that only accept layer inputs will work. It is not used to alter maps, otherwise almost every model would alter your maps.