Drop 20-30 grains of bird shot into the ferrule and pack it in lightly before you mount the head on the shaft. Or, get some of those little bullet weights that anglers use. A sixteenth ounce or 3/32 oz size should do it. Again, put one in nose/point first and tap it a bit to seat it before mounting the head to the shaft. You can also get them in tungsten, which is heavier than lead, meaning you can get more weight into a smaller package if that's what you need.
On the other hand, you could just shoot the Zwickeys as they are. You won't notice 25 grains difference in point weight.