Translate options in additional fields and text added with customizations

It is possible to do in two ways. Both ways is equal and upgrade proof (You do not lost this changes after upgrade to new version). You can choose the one that is easy implement for you.

Custom Language File

You can create language file specific for your installation and put translations to this file.

Create a custom language file amember/application/default/language/user/site/ru.php

ru should be replaced with a language code of desired language eg.: en, es, it, zn etc.

and add your translation to these file:

<?php

return [
    'one' => 'Один',
    'two' => 'Два'
];

Code in site.php

This method is more complex but have not any real advantage over first one.

Add this code to site.php file:

//set up array of translations
$translations_ru = [
    'one' => 'Один',
    'two' => 'Два'
];

//retrieve global translate object
$tr = Zend_Registry::get('Zend_Translate');
$locale = $tr->getLocale(); //save current active locale to temporary variable

//add your new translations
$tr->addTranslation([
    'adapter' => 'array',
    'content' => $translations_ru,
    'locale' => 'ru_RU',
]);

//restore locale to previous state
$tr->setLocale($locale);