Lyrically, "Zombie Bastards" addresses Weezer fans who are "stuck in the past" and who criticize them for changing their sound.[2] The song contains ska-influenced guitars, a dub bass, sampling and keyboards, which was described by Tom Breihan from Stereogum as "Weezer doing stadium-goth Spotify-core."[3] The song has been described as pop rock[4] and electropop.[5]
Randall Colburn at The A.V. Club gave "Zombie Bastards" a positive response, stating "...while as chintzy and overproduced as so much latter-day Weezer, has a cheeky, soaring chorus that should have even the dourest Pinkertonstans shouting along."[6] Emma Swann at DIY was more critical of the song, stating "‘Zombie Bastards’ is so childlike it'd be easy to question if it were intended for an infant audience if it wasn't for the, well, bastards."[7]
