Gzip is not working in aws lambda (Serverless)

Question

I am trying to zip the lambda response from java code but in browser it is failing to decode

    @Override
    public Map handleRequest(Map<String,Object> input, Context context) {

           Map<String, Object> repsonse = new HashMap<>();
           HashMap<String, String> headers = new HashMap<>();              
           headers.put("Content-Encoding", "gzip");
           headers.put("Content-Type", "text/html");
           final String sampleHtml = "<h1>Hello World</h1>";  
           ByteArrayOutputStream out = new ByteArrayOutputStream();
           GZIPOutputStream gzip = new GZIPOutputStream(out);
           gzip.write(sampleHtml.getBytes());
           gzip.close();
           String responseString = out.toString("ISO-8859-1");
           response.put("headers", headers);           
           response.put("body", responseString);
           response.put("statusCode", 200);
           response.put("isBase64Encoded", true);
           return response;
    }