quill/docs/_includes/full-editor.html

// Initialize editor with custom theme and modules
var fullEditor = new Quill('#full-editor', {
  modules: {
    'toolbar': { container: '#full-toolbar' },
  },
  theme: 'snow'
});

// Update basic editor's content with ours
fullEditor.on('text-change', function(delta, oldDelta, source) {
  if (source === 'user') {
    basicEditor.updateContents(delta);
  }
});

// Update our content with basic editor's
basicEditor.on('text-change', function(delta, oldDelta, source) {
  if (source === 'user') {
    fullEditor.updateContents(delta);
  }
});