If there is Zina between a man and his mother in-law before and after the marriage with her daughter. Is the relationship between the daughter and that man forbidden? Looking forward to hear from you as fast as you can.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Zina (fornication or adultery) is among the grave major sins and Allah threatens severe punishment for everyone who commits it.

Allah Says (what means): {And do not approach unlawful sexual intercourse. Indeed, it is ever an immorality and is evil as a way.} [Quran 17:32]

Allah also Says (what means): {And those who do not invoke with Allah another deity or kill the soul which Allah has forbidden [to be killed], except by right, and do not commit unlawful sexual intercourse. And whoever should do that will meet a penalty. Multiplied for him is the punishment on the Day of Resurrection, and he will abide therein humiliated.} [Quran 25: 68-69]

This threat is just for committing Zina; just imagine how much more severe it would be for the man who committed it with his wife's mother. It is mandatory upon a person to protect the honor of his wife's mother as he protects the honor of his mother and sister.

If Zina with a neighbour's wife comes in the third position following Kufr (disbelief) and killing one's child, then how harmful it would be if done with one's wife's mother. Ibn Mas’ood narrated that he asked the Prophet “O Allah's Apostle! Which is the biggest sin?” He said, “To set up rivals to Allah by worshipping others though He alone has created you.” I asked, “What is next?” He said, “To kill your child lest it should share your food.” I asked, “What is next?” He said, “To commit illegal sexual intercourse with the wife of your neighbor.”
Zina with one's neighbor's wife is considered so repulsive because a neighbor always expects from his neighbor that he will protect him and his family as well. And generally a neighbor trusts his neighbor. Thus violating his honor is high treason.
Moreover, practicing Zina with Mahaarim (unmarriageable persons) is not like Zina with others. The Prophet said: “Just kill the one who practises sex with his Mahram woman.” [Ibn Maajah]

Al-Baraa’ Ibn ‘Aazib said: “I met my uncle and a banner was with him, I asked: ‘Where are you heading? He replied: “The Prophet sent me to a person who has married the wife of his father, to kill him and to seize his property.” [Abu Daawood]

The Prophet ordered that the person who married his father's wife to be killed and his property to be taken as booty.

In your case, we conclude that you are obliged to separate from your wife since it is not permissible to marry a daughter and her mother at the same time. Marriage means having sexual relations. Since you had sex with the mother, it is not permissible for you to be (in marriage) with the daughter.

As for entering Paradise, it is possible if one makes sincere repentance and if the repentance is accepted by Allah; otherwise he will be subjected to the Will of Allah, Allah may forgive him or He may punish him. His matter is with Allah; Allah Says (what means): {And those who do not invoke with Allah another deity or kill the soul which Allah has forbidden [to be killed], except by right, and do not commit unlawful sexual intercourse. And whoever should do that will meet a penalty. Multiplied for him is the punishment on the Day of Resurrection, and he will abide therein humiliated - Except for those who repent, believe and do righteous work. For them Allah will replace their evil deeds with good. And ever is Allah Forgiving and Merciful.} [Quran 25: 68-70]

Allah knows best.