Usage for multi-property values on EntitySelect See https://gist.github.com/4352572

gistfile1.php

$this->add(array(
    'name'       => 'someName',
    'type'       => 'MyNamespace\Form\Element\EntitySelect',
    'attributes' => array(
        'required' => true
    ),
    'options'    => array(
        'label'          => 'Select element Label',
        'empty_option'   => '--- Choose Entity ---',
        'object_manager' => $this->getEntityManager(),
        'target_class'   => 'MyNamespace\Entity\TargetEntity',
        'property'       => array(
            'propertyOne',
            'propertyTwo'
        )
    )
));