public static int DiceSum4(IEnumerable<object> values)
{
    var sum = 0;
    foreach (var item in values)
    {
        switch (item)
        {
            case 0:
                break;
            case int val:
                sum += val;
                break;
            case IEnumerable<object> subList when subList.Any():
                sum += DiceSum4(subList);
                break;
            case IEnumerable<object> subList:
                break;
            case null:
                break;
            default:
                throw new InvalidOperationException("unknown item type");
        }
    }
    return sum;
}