Apache Zeppelin 0.7.3 - http error 503 in browser

The workaround was:

1. Install Java 8, following How to set or change the default Java (JDK) version on OS X?, i.e.

   brew tap caskroom/versions
   brew cask install java8
   export JAVA_HOME=`/usr/libexec/java_home -v 1.8`
   

2. Then:

   sudo bash
   zeppelin-daemon.sh start
   /Applications/Safari.app/Contents/MacOS/Safari
   

3. Point browser to: http://localhost:8080

Success! Conclusions:

1. Zeppelin 0.7.3 only supports Java <= 8.0

2. zeppelin-daemon.sh must be run as root, but browser doesn't have to be