If two effects change when Dahan in a land do Damage (e.g., Words of Warning and Warn of Impending Conflict), which one takes precedence?

If two effects change when Dahan in a land do Damage (e.g., Words of Warning and Warn of Impending Conflict), which one takes precedence?

Your choice. So in this example, the best outcome is usually applying Words of Warning first to make all Dahan do Damage at the same time as Invaders, and then using Warn of Impending Conflict to make some of those Dahan strike first. (If you applied them in the other order, then all Dahan would do Damage at the same time as Invaders, since Words of Warning would overwrite Warn of Impending Conflict.)
Overwriting a timing change doesn't overwrite any other part of the effect. The Event Engage on Their Own Terms will still reduce Dahan Damage even if something else changes when Dahan do Damage.