Dim parts As Integer = 4
Dim splittedCols As IEnumerable(Of IEnumerable(Of Integer)) =
     From index As Integer In Enumerable.Range(0, CInt(Math.Ceiling(mainCol.Count() / parts)))
     Select mainCol.Skip(index * parts).Take(parts)

dim combination as ienumerable(of integer) = splittedCols(Índice).Concat(splittedCols(Índice))

    ''' <remarks>
    ''' *****************************************************************
    ''' Snippet Title: Split Collection Into Parts
    ''' Code's Author: Elektro
    ''' Date Modified: 08-March-2015
    ''' Usage Example: 
    ''' Dim mainCol As IEnumerable(Of Integer) = {1, 2, 3, 4, 5, 6, 7, 8, 9}
    ''' Dim splittedCols As IEnumerable(Of IEnumerable(Of Integer)) = SplitColIntoParts(mainCol, amount:=4)
    ''' splittedCols.ToList.ForEach(Sub(col As IEnumerable(Of Integer))
    '''                                 Debug.WriteLine(String.Join(", ", col))
    '''                             End Sub)
    ''' *****************************************************************
    ''' </remarks>
    ''' <summary>
    ''' Splits an <see cref="IEnumerable(Of T)"/> into the specified amount of parts.
    ''' </summary>
    ''' <typeparam name="T"></typeparam>
    ''' <param name="collection">The collection to split.</param>
    ''' <param name="amount">The parts amount.</param>
    ''' <returns>IEnumerable(Of IEnumerable(Of T)).</returns>
    Public Shared Function SplitColIntoParts(Of T)(ByVal collection As IEnumerable(Of T),
                                                   ByVal amount As Integer) As IEnumerable(Of IEnumerable(Of T))
 
        Return From index As Integer
               In Enumerable.Range(0, CInt(Math.Ceiling(collection.Count() / amount)))
               Select collection.Skip(index * amount).Take(amount)
 
    End Function

        ' La colección principal.
        Dim mainCol As IEnumerable(Of Integer) =
            {
                1, 2, 3, 4,
                5, 6, 10, 15,
                20, 22, 24, 25,
                30, 35, 45, 47,
                50, 54, 57, 58,
                60, 67, 68, 69,
                70, 71, 75, 77,
                79, 80
            }

        ' La colección principal, dividida en una colección que contiene colecciones de 4 elementos (total: 8 colecciones).
        Dim parts As Integer = 4
        Dim splittedCols As IEnumerable(Of IEnumerable(Of Integer)) =
            From index As Integer In Enumerable.Range(0, CInt(Math.Ceiling(mainCol.Count() / parts)))
            Select mainCol.Skip(index * parts).Take(parts)

        ' Las 8 colecciones de 4 elementos cada una, unidas en una sola colección:
        Dim joinedCol As IEnumerable(Of Integer) = {}
        splittedCols.ToList.ForEach(Sub(col As IEnumerable(Of Integer))
                                        joinedCol = joinedCol.Concat(col)
                                    End Sub)

ListBox1.Items.AddRange(joinedCol.Cast(Of Object)().ToArray)