Series to consider:
Manga or Anime
Highschool of the Dead (MAIN)
Monster ga Afureru Sekai ni Natta Node, Suki ni Ikitai to Omoimasu (all monsters are zombies, grant people status system as the apocalypse starts, a bit sooner or later)
Zombie 100 ~Zombie ni Naru Made ni Shitai 100 no Koto~
Zombie Sekai de Harem wo Tsukurou!
Convenience Store of the Dead ~The Convenience Store Clerk Will Get Rescued in 100 Days~ (maybe its main female lead can be an ally due to her expected talent as scientist/researcher?)
Kingdom of Z (Maybe as a factionto help or allies?)
Tokyo Ghoul (difficulty multiplier, but only ghouls as zombies, SUPER MUTANTED ZOMBIES)
Games
OneeChanbara series (Check it out)
The House of the Dead: Overkill (Check it out)
Lollipop Chainsaw (Figure it out)
Plants vs. Zombies (As a tinker, plants only, sexy version)
Dead Island series (Check these out)
Dead Rising (Check it out)
Telltale's The Walking Dead (Check it out)
Resident Evil series (difficulty multiplier)
Dead Space (HUGE difficulty multiplier, but only for last few arcs)
Left 4 Dead series (small difficulty multiplier)
Dying Light (Check it out)
Dead Island (Check it out)
The Callisto Protocol (Check it out)
The Evil Within (Check it out)
The Last of Us (Check it out)
Movies
World War Z
Other Worlds Using GATE from its source: the manga/anime with GATE in name.
LATER. TO BE CONSIDERED.