I suggest you should start off with either polygon or sub-D to build the basic shape of the model first, then add the details in Z-brush later. It seems like you tried to add details before you have the basic features down. Anyway, good work and keep up the effort!! Add oil!!!
I think the eyes of your model is a little bit too big. The jaw bone could be wider, the back of his neck is a little "thin" you can move it back a bit. And also pay attention to his nose bridge, it needs to wider.