Retrieving email attachment (Zip File) then unzipping and adding back all the extracted files to the same email- CRM 2013

// Retrieve all attachments associated with the email activity.
                    QueryExpression _attachmentQuery = new QueryExpression
                    {
                        EntityName = ActivityMimeAttachment.EntityLogicalName,
                        ColumnSet = new ColumnSet(true),
                        Criteria = new FilterExpression
                        {
                            Conditions =
                        {
                            new ConditionExpression
                            {
                                AttributeName = "objectid",
                                Operator = ConditionOperator.Equal,
                                Values = {_emailId}
                            },
                            new ConditionExpression
                            {
                                AttributeName = "objecttypecode",
                                Operator = ConditionOperator.Equal,
                                Values = {Email.EntityLogicalName}
                            }
                        }
                        }
                    };

                    EntityCollection results = _serviceProxy.RetrieveMultiple(
                        _attachmentQuery);
       foreach (ActivityMimeAttachment a in ec.Entities)
        {
        string strcontent = a.body;

Can someone guide me how I unzip from here...

            string zipPath = @"c:\example\start.zip";
            string extractPath = @"c:\example\extract";

            using (ZipArchive archive = ZipFile.OpenRead(zipPath))
            {
                foreach (ZipArchiveEntry entry in archive.Entries)
                {
                    if (entry.FullName.EndsWith(".xml",       StringComparison.OrdinalIgnoreCase))
                    {
                        entry.ExtractToFile(Path.Combine(extractPath, entry.FullName));
                    }
                }
            } 

 I tried with the above code using console app but I like to use .net 4.0 framework.How to unzip and attach to the same email.Please guide me.