Pretty well done, could be better though...
Since I am a fan of zombie games, I can definitely say you accomplished what you were trying to achieve in regards to the theme of this song.
However.. the song feels as though its lacking diversity, although the general tune of the chimes/bass give that good eerie tone to the song, you don't really have anything that gives a strong sense of horror. (you can disregard what I'm gonna say if that's not what you were aiming for) As for a way to improve that... well there's no obvious way, because adding more intense beats would probably make this song more cliche compared to similar songs of this category.
Never the less, you did a nice job composing this, it sticks out from the usual zombie apocalypse songs but still manages to have the same feeling.