You can charge it on a zzmt controller, but the zzmt is a 2 cell whereas the zz is one. There is a resistance on the cell in the zz's that creates a resistance for the current to flow. Running 4 batteries is going to double the amount of current through the cell in your zz that if it were on a regular controller. It might work now, but you are going to negatively affect that cell in the long run.