[Kromm]

The close-range rule amounts to saying "treat it as a slug with an armor divisor of (0.25)." So the correct comparison is 9 × 1d+1 pi vs. 4d+4(0.25) pi++. Zombies have DR 0, which becomes DR 1 against attacks with a divisor less than 1 (p. B379). Zombies also have IT (Unliving), which means that pi++ does ×1 injury while pi does ×1/3 (p. B380). In essence, then, each 1d+1 pi hit inflicts on average (3.5 + 1)/3 = 1.5 points of injury; if all nine hit, that's 13.5 points. The 4d+4(0.25) pi++ hit inflicts on average 4×3.5 + 4 - 1 (for DR) = 17 points of injury. I'd say that the close-range blast is better.