using System;

using System.IO;

using ICSharpCode.SharpZipLib.Zip;

public class Program

{

    public static void Main()

    {

        string zipFileBase64 = "UEsDBAoAAAAAAOaLllKXePD9nQAAAJ0AAAAIAAAAdGVzdC56aXBQSwMEFAAAAAgA5IuWUoamEDYHAAAABQAAAAgAAAB0ZXN0LnR4dMtIzcnJBwBQSwECHwAUAAAACADki5ZShqYQNgcAAAAFAAAACAAkAAAAAAAAACAAAAAAAAAAdGVzdC50eHQKACAAAAAAAAEAGADr1dfXUTfXAevV19dRN9cBO+ek1VE31wFQSwUGAAAAAAEAAQBaAAAALQAAAAAAUEsBAh8ACgAAAAAA5ouWUpd48P2dAAAAnQAAAAgAJAAAAAAAAAAgAAAAAAAAAHRlc3QuemlwCgAgAAAAAAABABgAQCwc21E31wFALBzbUTfXAdiPG9tRN9cBUEsFBgAAAAABAAEAWgAAAMMAAAAAAA==";

        using (var zipStream = new MemoryStream(Convert.FromBase64String(zipFileBase64)))

        using (var zip = new ZipFile(zipStream))

        {

            var nestedZipEntry = zip.GetEntry("test.zip");

            using (var nestedZipStream = zip.GetInputStream(nestedZipEntry))

                using (var nestedZip = new ZipFile(nestedZipStream))

            {

                var fileEntry = nestedZip.GetEntry("test.txt");

                using (var fileStream = nestedZip.GetInputStream(fileEntry))

                    using (var reader = new StreamReader(fileStream))

                {

                    Console.WriteLine(reader.ReadToEnd());

                }

            }

        }

    }

}