Fast clear an array

[hennyere]

HI, guys!

I have one question:

Private Type udtCell
    nAlignment As Integer
    nFormat As Integer
    nFlags As Integer
    sValue As String
    sTag As String
    lCellData As Long
    pPic As StdPicture
    IsSized As Boolean
End Type
Private Type udtItem
    lHeight As Long
    lImage As Long
    lItemData As Long
    nFlags As Integer
    sTag As String
    bGroupRow As Boolean
    bVisible As Boolean
    Cell() As udtCell
End Type
Private Declare Sub ZeroMemory Lib "kernel32" Alias "RtlZeroMemory" (ByRef Destination As Any, ByVal Length As Long)

Private Sub Command1_Click()
    Dim x() As udtItem, y() As udtItem, z() As udtItem, I As Long, L As Long
    For I = 0 To 100000
        ReDim Preserve x(I) As udtItem
        x(I).bVisible = True
        x(I).lHeight = 42
        x(I).sTag = "Number " & I
        'x(I).Cell.nAlignment = 0
    Next
    L = Timer
    ReDim x(0) As udtItem
    Debug.Print "Using ReDim: " & (Timer - L)
    
    For I = 0 To 100000
        ReDim Preserve y(I) As udtItem
        y(I).bVisible = True
        y(I).lHeight = 42
        y(I).sTag = "Number " & I
        'y(I).Cell.nAlignment = 0
    Next
    L = Timer
    Erase y
    Debug.Print "Using Erase: " & (Timer - L)
    
    For I = 0 To 100000
        ReDim Preserve z(I) As udtItem
        z(I).bVisible = True
        z(I).lHeight = 42
        z(I).sTag = "Number " & I
        'z(I).Cell.nAlignment = 0
    Next
    L = Timer
    'How can I implement ZeroMemory to clear z() array???

    ZeroMemory z(0), Ubound(z) + 1 = VB CRASHES!

    Debug.Print "Using ZeroMemory: " & (Timer - L)
    
End Sub