Connected.Components/Styles/utilities/layout/_zindex.scss

$count: 1;
$value: 0;

@while $count < 12 {
  .z-#{$value} {
    z-index: $value;
  }
  $count: $count + 1;
  $value: $value + 10;
}

.z-auto{
  z-index:auto;
}