You're misusing Buffs_BuffPower here. It should scale damage multipliers relative to 1.0, so that you deal 100% damage at 0 buff power, or gain half the benifit of the multiplier at 0.5 buff power. Consider this
```
float mult = 1.0 + (cvar("g_buffs_zen_factor") - 1.0) * Buffs_BuffPower(a, BUFF_ZEN);
```