At present, the kafka-server-start.sh and zookeeper-server-start.sh will start kafka broker and zookeeper in fg mode, though "daemon" parameter is added. you need to add & to make it bg. But the console log will still output in fg.
Should make it fully run in bg and redirect console log to files. And log file position should not depends on where the cmd is running. Thus it will be more friendly for scripts to launch server on nodes by batch.