What Zoroastrianism says about balance
A warning first, because this is the tradition most likely to be misread on the subject. Zoroastrianism does not balance good against evil, and it expects one to defeat the other. Its balance sits elsewhere: in moderation, in the agreement of thought with word and deed, and in a refusal to rank spirit above body. These nine concepts show where the level is meant to be held.
Moderation
Excess is faulted in food, drink and pleasure, and in religious practice too. The middle path is named as the righteous one, not merely the safe one.
Traditional
Unity of the Three
Thinking one thing, saying a second and doing a third is what falsehood looks like in daily life. Integrity is described as three things lining up.
Traditional
Haurvatat - Wholeness and Health
Haurvatat is wholeness, and it covers the body's health as well as the spirit's. Being complete is treated as the intended state rather than a reward.
Avesta
Body and Soul
Body and soul are held to be partners. The complete person includes both, which is why the resurrection expected here is a bodily one.
Anthropology
The Physical World
Matter is not the problem. The world is a good creation that has been damaged, and the task is to repair it rather than escape it.
Cosmology
Happiness as Goal
Happiness is a legitimate aim, and it is said to arrive by making others happy. There is no premium on self-denial in this tradition.
Gathas
Wealth and Poverty
Wealth honestly acquired is approved of, and care for the poor is required. Both extremes are named as working against the good.
Economic Ethics
Care for Creation
Looking after the natural world is a duty rather than a preference. The reasoning is simple: it is the good creation, and it is under attack.
Vendidad
Fire and Water
Fire and water are the two elements held most sacred, and both must be kept from pollution. The rituals for them run in parallel.
Element Veneration
So the balance here is always inside the good, never between good and something else. A Zoroastrian is asked to eat moderately, work hard, keep the water clean and be happy, all at once. Where some traditions ask for less life, this one asks for it in proportion.