Steven…watch the zsphere scripts that come with z2 and definitely check out the practical guide both will help ya alot.
To edit zsphere mesh set your density to highest level your computer can handle then go to geometry and use the subd’s to model the mesh. if you add or subtract zspheres you will lose the work on the mesh you did.
see the scripts for how to save your work with morph targets so you don’t lose hours of work for nuttin.
PS. your fish looks good to me! have fun with z2.