Zend_Form_Element_File label is not translated when the form element is rendered separately.

example:

// controller
$form = new Zend_Form();
$form->setEnctype('multipart/form-data');
$form->addElement('file', 'myFile', array('label' => 'fileLabel', 'required' => false));
$form->addElement('text', 'myText', array('label' => 'textLabel', 'required' => false));
$form->addElement('submit', 'mySubmit', array('label' => 'submitLabel'));
$this->view->form = $form;

// view
<?= $this->form->renderForm(false) ?>
<?= $this->form->myFile ?>
<?= $this->form->myText ?>
<?= $this->form->mySubmit ?>

"textLabel" and "submitLabel" are correctly translated, "fileLabel" is not translated.

If the form is rendered in such a way:

// view
<?= $form ?>

then all labels are translated correctly.