I don't think it is possible to increase both. Since the total power output of the cell is governed by the types and amounts of chemicals inside the cell, the only thing that Zapping can do is exchange one for the other.
By zapping, the internal physical structure of the anode is changed to reduce internal resistance, thus increasing output voltage at the expense of runtime.
Higher voltage output, but reduced run time= the same TOTAL NET power output of the cell.
When I say Types and amounts of chemicals, I say this because during the manufacturing process, some cells receive more or less of any given chemical, whether its in the electrolytic solution, or in the anode and cathode. Variance in tolerance of each of these factors change the discharge characteristics of the cell. That is why "Matching" is important; to group similar cells together, so no one cell is going dead before the others, and thus becoming damaged from reverse charge polarity (that is what happens when one cell is dead, and the other 5 are still going)
So, long story short, You must trade one for the other.