RadFlowDocument flowDocument;
using (Stream str = new FileStream("input.docx", FileMode.OpenOrCreate))
{
    MemoryStream ms = new MemoryStream();
    str.CopyTo(ms);
    ms.Seek(0, SeekOrigin.Begin);

    using (ZipArchive archive = ZipArchive.Update(ms, null))
    {
        var zipEntries = archive.Entries;

        // Skip glossary on importfor (int i = zipEntries.Count() - 1; i >= 0; i--)
        {
            var entry = zipEntries.ElementAt(i);
            string entryName = entry.FullName;
            if (Regex.IsMatch(entryName, @"\[trash\]"))
            {
                entry.Delete();
            }
        }
    }
}