Clustering Dockerized Elasticsearch with multiple Docker Host

Trying to make it clustering with docker compose.
I have two elasticsearch docker containers which are deployed in different Docker Hosts.

docker-compose.yml for docker-container-1

services:
  elasticsearch:
    restart: always
    hostname: elasticsearch
    image: docker-elk/elasticsearch:1.0.0
    build:
      context: elasticsearch
      dockerfile: Dockerfile
    environment:
      discovery.type: zen
    ports:
      - 9200:9200
      - 9300:9300
    env_file:
      - ./elasticsearch/elasticsearch.env
    volumes:
      - elasticsearch_data:/usr/share/elasticsearch/data

docker-compose.yml for docker-container-2

services:
  elasticsearch:
    restart: always
    hostname: elasticsearch
    image: docker-elk/elasticsearch:1.0.0
    build:
      context: elasticsearch
      dockerfile: Dockerfile
    environment:
      discovery.type: zen
    ports:
      - 9200:9200
      - 9300:9300
    env_file:
      - ./elasticsearch/elasticsearch.env
    volumes:
      - elasticsearch_data:/usr/share/elasticsearch/data

elasticsearch.yml on the elasticsearch-docker-container-1 on the Docker-Host 1

xpack.security.enabled: true
cluster.name: es-cluster
node.name: es1
network.host: 0.0.0.0
node.master: true
node.data: true
transport.tcp.port: 9300
path.data: /usr/share/elasticsearch/data
path.logs: /usr/share/elasticsearch/logs
discovery.zen.minimum_master_nodes: 1
gateway.recover_after_nodes: 1
discovery.zen.ping.unicast.hosts: ["host1:9300", "host2:9300","host1:9200", "host2:9200"]
network.publish_host: host1

elasticsearch.yml on the elasticsearch-docker-container-2 on the Docker-Host 2

xpack.security.enabled: true
cluster.name: es-cluster
node.name: es2
network.host: 0.0.0.0
node.master: true
node.data: true
transport.tcp.port: 9300
path.data: /usr/share/elasticsearch/data
path.logs: /usr/share/elasticsearch/logs
discovery.zen.minimum_master_nodes: 1
gateway.recover_after_nodes: 1
discovery.zen.ping.unicast.hosts: ["host1:9300", "host2:9300","host1:9200", "host2:9200"]
network.publish_host: host2

Below is the result of GET /_cluster/health?pretty and it shows that there is only one node.

{
  "cluster_name" : "dps_geocluster",
  "status" : "yellow",
  "timed_out" : false,
  "number_of_nodes" : 1,
  "number_of_data_nodes" : 1,
  "active_primary_shards" : 33,
  "active_shards" : 33,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 30,
  "delayed_unassigned_shards" : 0,
  "number_of_pending_tasks" : 0,
  "number_of_in_flight_fetch" : 0,
  "task_max_waiting_in_queue_millis" : 0,
  "active_shards_percent_as_number" : 52.38095238095239
}

According to the document below at least three elasticsearch nodes are required.
https://www.elastic.co/guide/en/elasticsearch/reference/6.5/modules-node.html

Each elasticsearch container should be at different Docker host?

Thank you.