The people hostile to religion always tried to slander prophets - This is not happened to Prophet Muhammed alone.Look at one of the mightiest prophet of Old testament - DAVID
But the jews have writeen using their own hands that David was seduced by a bathing women and committed adultery
Check this in BIBLE Samuel 11:1
A legitimate Question How come DAVID which the bible says as a prophet be a adulterer? This perverted version of the event got into bible because there is no systematic way of filtering historical events and those who want to justify their acts (esp priests) managed to attribute such heinious things to him.
It is the same kind of evil people who attriuted the samething to Muhammed that he watched zainab when she was bathing. But neither quran nor hadith says this, only some junk biograpgy written after many centuries has this story. But the fascination of islam crtics that anything which has a arabic name must be infalliable islmic source is a ridiculous proposition.