Disclaimer: I know nothing about Harry’s relationships. All of these posts are based on my personal opinion and informed by the videos and photos and information we have that has been made publicly available, especially Harry’s music.
Harry is not a womanizer or a manwh*re and eff anyone who claims that in a desperate attempt to denigrate him or victimize someone else. He has shown above and beyond that only one person resides in his heart and has for years.
In Zayn vs anyone, Zayn always wins.
Bottom line: Harry seems to grow bored of everyone who passes through his life (apart from his inner circle) both romantically and sometimes those who come and go platonically…but not Zayn. Even after all those years, in 2018, he emphatically told Zayn he was Still The One.