Full Idea
Zeno (like Plato) admits a plurality of specifically different virtues, namely prudence, courage, sobriety, justice, which he takes to be inseparable but yet distinct and different from one another.
Gist of Idea
Zeno says there are four main virtues, which are inseparable but distinct
Source
report of Zeno (Citium) (fragments/reports [c.294 BCE]) by Plutarch - 70: Stoic Self-contradictions 1034c
Book Reference
Plutarch: 'Moralia - vol 13 part 2', ed/tr. Cherniss,Harold [Harvard Loeb 1993], p.425
A Reaction
In fact, the virtues are 'supervenient' on one another, which is the doctrine of the unity of virtue. Zeno is not a pluralist in the way Aristotle is - who says there are other goods apart from the virtues.