I have hanging Zinc anodes connected to protect my aluminum hull. Why is the hull still corroding?

Aluminum hulls are GREAT conductors and are the least "Noble" metal in contact with any water. To have a metal "LESS" noble than the hull you'll need to be using "Magnesium" anodes. This is a less noble metal to your hull. But if you have the correct paint (which you do not) on the hull, you would not have two things going on. 1. Hull corrosion 2. Barnacles growing on the hull. Both of these conditions tell me that you have the "WRONG" coatings applied, period. If you had the correct coatings, you'd have neither happening. The coatings need to have an "Growth Inhibitor" minimize marine growth of all forms. Zinc is a harder metal than Aluminum, so that's why you have the corrosion. Sounds like you're using this boat in saltwater. Not the best material to start with either. Any kind of defect in the coating will allow "Electrolysis" to enter to mixture. But, you'll still have some due to the rudder, drive shafts, water pickups, and scuppers. You must also find the electrical "Leak" causing this problem too. There's always going to be some leakage, but you seem to have an excess leakage to cause the hull problem.