In the Zero-Sum scenario, the encounter matrix cell payoffs for each Agent are absolutely opposite (Payoff Correlation = -1.00).  No matter what Agent choices are made, a Self-Gain of 1 point requires an Other-Loss of 1 point.  The inevitable consequence of any choice is that Self-Gain (or Loss) must be accompanied by an equal Other-Loss (or Gain).  This scenario is somewhat more interesting than Utopia, but it still offers only a limited scope for examining ethical decisions.  The imperative for survival (Self-Gain) makes it impossible to offer gain to Other-Agent.

There are several consequences for ethics metrics:

Self-Gain and Other-Gain after an encounter are always of opposite value.

Commonwealth after an encounter will always be zero.

Any Self-Gain that differs from zero will automatically yield Inequality (less Equality).  The only way to avoid Inequality is to make no gain or loss.

Any gain in Commonwealth is impossible, so ironically, the only way to maximize Total Ethics is to maximize Equality.

Because Commonwealth is unvarying, Total Ethics is determined solely by Equality.

The Zero-Sum scenario is more interesting than the Utopia scenario because there are two, not one, measures of interest.  In Utopia, all measures of ethics were derived from one factor - Self-Gain.  In Zero-Sum, we have two independent factors - Self-Gain and Equality.

The single factor influencing Self-Gain was Basic Strategy.  Altruism (either Good/Bad Will or Reciprocity) had no effect on Other-Gain, Commonwealth or Equality.

The rank order of Self-Gain for the Basic Strategies was:

The first five strategies eked out positive average Self-Gains.  The final four strategies suffered negative average Self-Gains.

The rank order for Other-Gain was inevitably the reverse of Self-Gain.  Winning Self-Gain strategies caused losses for the Other-Agent; losing Self-Gain strategies caused gains for the Other-Agent.

Total Ethics is solely determined Equality.  This rank, from most Equal to least Equal (and most ethical to least ethical) was: