How can the concept of "adultery of the eye" mentioned in the Hadith ("Indeed, the adultery of the eye is a lustful gaze") be reconciled with the Hadith of the Prophet seeing a beautiful woman and then going to Zaynab, and how can one respond to those who deny the concept of "adultery of the eye" in Islam?

It is not necessary to invalidate something attributed to Christianity or Judaism; rather, it should be presented to the Islamic revelation and law. What conforms to it is accepted, what contradicts it is rejected, and what is unaddressed remains unaddressed—it is neither affirmed nor denied. The Shari'ah indeed found corroboration for the Christian saying that looking at a non-mahram woman is the fornication of the eyes, as stated in the authentic Hadith: "The fornication of the eyes is gazing." As for the story of the Prophet, peace be upon him, seeing a woman and then going to Zaynab, the narration is weak in its story. Even if it were authentic, the blameworthy gaze is the intentional gaze of lust, not the unintentional, sudden glance. The Prophet, peace be upon him, commanded turning away the gaze from a sudden glance. The Prophet, peace be upon him, did what he did due to the perfection of his preservation, the purity of his heart, and his eagerness for his heart to remain pure.