Group numbers in two columns using collections

Hello everyone
I have a working code that groups the numbers in column B and this is the code

Sub Test()
    Dim z           As New Collection
    Dim a           As Variant
    Dim b           As Variant
    Dim v           As Variant
    Dim w           As Variant
    Dim str1        As String
    Dim i           As Long
    Dim j           As Long
    Dim k           As Long

    a = Range("A2:C" & Cells(Rows.Count, 1).End(xlUp).Row).Value
    
    For i = 1 To UBound(a, 1)
        str1 = a(i, 1)
        On Error Resume Next
            z.Add Key:=str1, Item:=Array(a(i, 1), New Collection)
        On Error GoTo 0
        z(str1)(1).Add a(i, 2)
    Next i
    
    ReDim a(1 To z.Count, 1 To 2)
    i = 0
    
    For Each v In z
        i = i + 1
        a(i, 1) = v(0)
        j = 0
        ReDim b(1 To v(1).Count + 1)
        For Each w In v(1)
            j = j + 1
            b(j) = w
        Next w
        For j = 1 To UBound(b) - 2
            For k = j + 1 To UBound(b) - 1
                If b(k) < b(j) Then
                    w = b(j)
                    b(j) = b(k)
                    b(k) = w
                End If
            Next k
        Next j
        a(i, 2) = b(1)
        j = 1
        For k = 2 To UBound(b)
            If b(k) <> b(k - 1) + 1 Then
                If j = k - 1 Then
                    a(i, 2) = a(i, 2) & " | " & b(k)
                Else
                    a(i, 2) = a(i, 2) & "-" & b(k - 1) & " | " & b(k)
                End If
                j = k
            End If
        Next k
        a(i, 2) = Left$(a(i, 2), Len(a(i, 2)) - 3)
    Next v
    
    Application.ScreenUpdating = False
        Range("F2").Resize(UBound(a, 1), UBound(a, 2)).Value = a
    Application.ScreenUpdating = True
End Sub

How can I group the column C too to have it grouped in column H?