Is the guardianship of the father, who is in a state of Ihram, forfeited if he sexually assaults his daughter, and does her marriage become void?

The father's sexual assault on his daughter is a perversion of the natural human disposition (fitra). If the father repents and regrets, his guardianship remains valid. However, if he does not repent and does not regret, his guardianship remains valid as long as he is trustworthy towards her, regardless of his transgression, according to Sheikh Ibn Uthaymeen's statement. If he is not trustworthy, then the guardianship transfers to the next in line among the guardians. Your previous marriage, conducted by your father, is valid. As for what was reported from Imam Ahmad regarding the separation between a Zoroastrian brother and his Muslim sister, it is because Zoroastrians deem incestuous marriages permissible, and the difference in religion prevents a disbeliever from having guardianship over a Muslim woman.