I think the author is confused as to where to take the story and is keep getting her plot lines mixed up.
The author is not following a linear timeline the story is clearly bouncing around as far as the timeline goes. Yes Zero died but that was way after Yuki gave birth to Ren.
Zero is still alive and Ren's hair is still long so It's a flashback. I'll happen often in this manga.
Zero and Yuki are both dead in Ren and Ai's present time with Kaname.
The manga is called "memories" c'mon now.
I'm still so confused??I thought Zero died while he was protecting Yuki and now he is alive after his daughter born im like?? Did I skip chapter,,, im really confused