Is it possible to encode byte array into readable string in case of XLSX format?

XPathDocument document = new XPathDocument(@"infopathform.xml");
XPathNavigator navigator = document.CreateNavigator();

//Get the my namespace URI
navigator.MoveToFollowing(XPathNodeType.Element);
string myNamespace = navigator.GetNamespacesInScope(XmlNamespaceScope.All)["my"];

//Create an XmlNamespaceManager
XmlNamespaceManager ns = new XmlNamespaceManager(new NameTable());
ns.AddNamespace("my", myNamespace);

//Create an XPathNavigator object for the attachment node
XPathNavigator xnAttNode = navigator.SelectSingleNode("//my:Attachments", ns);

//Get the encoded value as string
string encodedAttachment = xnAttNode.InnerXml;

byte[] theData = Convert.FromBase64String(encodedAttachment);

using (MemoryStream ms = new MemoryStream(theData))
{
    BinaryReader theReader = new BinaryReader(ms);

    //Position the reader to obtain the file size.
    byte[] headerData = new byte[16];
    headerData = theReader.ReadBytes(headerData.Length);

    int fileSize = (int)theReader.ReadUInt32();
    int attachmentNameLength = (int)theReader.ReadUInt32() * 2;

    byte[] fileNameBytes = theReader.ReadBytes(attachmentNameLength);
    //InfoPath uses UTF8 encoding.
    Encoding enc = Encoding.Unicode;
    string attachmentName = enc.GetString(fileNameBytes, 0, attachmentNameLength - 2);
    byte[] decodedAttachment = theReader.ReadBytes(fileSize);
}

using (MemoryStream memoryStream = new MemoryStream(decodedAttachment))
{
    ZipArchive zip = new ZipArchive(memoryStream, ZipArchiveMode.Read);
    foreach (var entry in zip.Entries)
    {
        //do something with each XML file
        var sw = new StreamReader(entry.Open());
        string xmlString = sw.ReadToEnd();
    }
}

using (MemoryStream memoryStream = new MemoryStream(decodedAttachment))
{
    ZipPackage p = (ZipPackage) ZipPackage.Open(memoryStream);
    foreach (var part in p.GetParts())
    {
        var s = new StreamReader(part.GetStream());
        string xmlString = s.ReadToEnd();
    }
}

using (MemoryStream memoryStream = new MemoryStream(decodedAttachment))
{
    SpreadsheetDocument document = SpreadsheetDocument.Open(memoryStream, false);
    foreach (var worksheetPart in document.WorkbookPart.WorksheetParts)
    {
        //do something with all worksheets
    }
}