Code:
Private Sub Unzip(ByVal filename As String)
    Dim inputStream As New ZipInputStream(File.OpenRead(filename))
    Dim entry As ZipEntry = Nothing
    Dim nBytes As Integer = 2048
    Dim data As Byte() = New Byte(2047) {}
    
    While (entry = inputStream.GetNextEntry()) IsNot Nothing
        If entry.Name.ToUpperInvariant().EndsWith("ZIP") Then
            Dim ms As New MemoryStream()
            While (nBytes = inputStream.Read(data, 0, data.Length)) > 0
                ms.Write(data, 0, nBytes)
            End While
            ms.Position = 0
            
            Dim tempStream As New ZipInputStream(ms)
            Dim tempEntry As ZipEntry = Nothing
            
            While (tempEntry = tempStream.GetNextEntry()) IsNot Nothing
                Dim nBytes2 As Integer = 2048
                Dim data2 As Byte() = New Byte(2047) {}
                While (nBytes2 = tempStream.Read(data2, 0, data2.Length)) > 0
                    ResultBox.AppendText(New ASCIIEncoding().GetString(data2, 0, nBytes2))
                End While
            End While
        End If
    End While
    inputStream.Close()
End Sub
habe diesen Code grade dank google gefunden.
Ich weis nicht ob es geht aber dem ein oder anderen hilft es bestimmt.

mfG