Even if my answer is late...
I also don't think the zombie is his boyfriend...
Because of the appearance firts but also 'cause apparently his boyfriend know how to drive a car him...
The zombie have some memories about his past life and he know that he was unable to drive that car. (for exemple he remembers that he know how to cook)
Moreover in the 1st chapter his boyfriend lost a different eye than the zombie ╮( ̄▽ ̄)╭
http://www.mangago.me/read-manga/boyfriend_of_the_dead/nmt/c016/26/
"Rich Boyfriend: Zombified and Smashed"
That's all I have to say ╮( ̄▽ ̄)╭
Wait I'm reading some comments and they are saying that this zombie is her bf but he's not cuz at the beginning when she pounded her bf he was somewhere else on the same day I know this cuz after she beat her ex she was like where's the nearest store and then they met so I'm confused on what ppl are saying explain plz