#available-zones{display: flex;flex-wrap: wrap;}
#available-zones .zone{background: white;padding: 15px;width: calc(25% - 15px);margin-bottom: 15px;margin-right: 15px;border-bottom-right-radius: 15px;}
#available-zones .zone h4{ margin-top: 0; }
#available-zones .zone:nth-child(4n){ margin-right: 0; }

@media only screen 
  and (min-device-width: 375px) 
  and (max-device-width: 812px)
{ 
    #available-zones{flex-wrap: wrap;}
#available-zones .zone{width: 100%;margin-right: 0;}
#available-zones .zone h4{  }
#available-zones .zone:nth-child(4n){  }
}