While the idea that there must be some ultimate justice beyond death is attractive for various reasons it does not automatically follow that it is true. Furthermore, it does not automatically follow that the idea is Zoroastrian.
There are historically speaking two roads to the concept of ultimate justice:
One path is the Judeo-Christian-Muslim one which teaches that ultimately there is a judgment day when justice is restored and each historical act is balanced against every other historical act in a zero-sum game. This is the job of The Judge-God-Father of the Abrahamic faiths. We have no such judge in Zoroastrianism. Consequently, we do not share this belief. Because we have no foundation on which to base such a belief.
The second path is the concept of karma in Hindu thought. What you do in this life decides where you end up in your next life. We have no such concept in Zoroastrianism either. Rather, this division is the most dramatic difference between historical Hinduism and historical Zoroastrianism. Instead of karma, the concept of ASHA is the focal point of Zoroastrianism. We don't deal in fake tomorrows, instead we are obsessively involved with the here and now, which we hold sacred!
The point is that NONE of these concepts of ultimate justice were historically constructed to solve the issue of justice but rather to force a peasant labor force to submit to a ruling aristocracy in a feudal society. Karma was always the excuse of the wealthy in India to go on with their wealthy lives keeping the poor in their place. It explains why India was always one of the most conservative (and ironically the most unjust) cultures on the planet. The Middle Eastern and European landowners associating themselves with synagogues, chuches and mosques was their way of staying in power keeping the poor masses in their places. "Life may look unjust now, but just wait until judgment day in the heavens when justice will be restored". Except that no such heaven ever happened. The cheapest possible way of keeping the poor supressed.
This is precisely why we as Zoroastrians should keep resisting such cheap concepts of ultimate justice. Because they are made the deceived people from the truth. Justice is restored and can only be restored in the here and now, in the CURRENT life which we live here and now, and as Zoroastrians love and enjoy and hold sacred.
And while many would love wrong-doers to have guilty conscience, we know for a fact from modern psychology that this may not be the case at all. Many destructive people do not feel any guilty conscience whatsoever. We need to keep wishful thinking away from scientific facts if we want to be taken seriously. Rather, Zarathushtra teaches that we PERCEIVE ourselves to be the actions we undertake. That is not the same thing as an automatic return to ultimate justice. We are just going to face the fact that ultimate justice does not exist, what exists is the justice that we ACHIEVE to create. It is up to us to achieve justice and not to anybody else. That is the Zoroastrian attitude towards justice.