ABUnzip doesn't work!

Sub Globals
   'These global variables will be redeclared each time the activity is created.
   'These variables can only be accessed from this module.
    Dim FTP As FTP
   Dim BtInvia As Button
   Dim BtRicevi As Button
   Dim EditText1 As EditText
   Dim sdRoot As String
   sdRoot = Main.sdRoot (it comes from the main activity module: sdRoot = File.DirRootExternal & "/")
   Dim Nfile As String
   NFile = "1.zip"
End Sub

Sub Activity_Create(FirstTime As Boolean)
   Activity.LoadLayout("Sync")
    If FirstTime Then
          FTP.Initialize("FTP", "192.168.1.91", 21, "emmeci", "emmeci")
   End If
End Sub

Sub BtRicevi_Click
   Dim myZip As ABZipUnzip
   Msgbox("download started","ready!")
   File.MakeDir(sdRoot, "mcordini")
   File.Delete(sdRoot,NFile)
   FTP.List("/")
   FTP.DownloadFile(NFile, False, sdRoot, NFile)
   myZip.ABUnzip(sdRoot & NFile, sdRoot & "mcordini")
End Sub