i'm not too sure about the motorcycle and mc going back in time aspect but this manhua does have an arc with zombies and the love interest was the protagonist's younger sibling in his first life
https://www.mangago.zone/read-manga/i_have_to_be_a_great_villain/
no that isnt it sadly (i have read that though!!) it was fully revolved around zombies not just a portion
Maybe Corrosive
nope not that one either ┗( T﹏T )┛(iv also read that one lmao)
i read it a lonnng while ago omg
all i rember is that its a zombie apoc bl (could be yaoi could not i dont rember)
and the mc can like go back in time when he dies or can sense danger or something like that hurrhgngn
the love interest has a younger sibling
theres a scene where the love interest is sick and the mc almost puts a booty pill in his butt for him.
theres motorcycles....the love interest is cold... AAHAHAHAFHFFHF PLEASE HELP ME!! （/TДT)/