hugo-theme-zzo/assets/sass/themes/_theme.scss

@import 'dark';
@import 'light';
@import 'hacker';
@import 'solarized';
@import 'custom';

$themes: (
  dark: $dark,
  light: $light,
  hacker: $hacker,  
  solarized: $solarized,
  custom: $custom,
);