My tests:
Fresh install: ZenTaoALM.12.5.3.int.zip
Default language: English

Added a new language:
Language: Russian
Code: ru
Reference Language: English

Below menus and errors:
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Dashboard -> Home

Project Report
17:48:10 syntax error, unexpected 'If' (T_IF) in module/task/lang/ru.php on line 183 when visiting /index.php?m=my&f=index
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Dashboard -> Task
17:48:45 syntax error, unexpected 'If' (T_IF) in module/task/lang/ru.php on line 183 when visiting /index.php?m=my&f=task

Dashboard -> Bug
17:49:03 syntax error, unexpected 'change' (T_STRING) in module/bug/lang/ru.php on line 164 when visiting /index.php?m=my&f=bug

Dashboard -> Project
17:49:22 syntax error, unexpected 'Default' (T_DEFAULT) in module/project/lang/ru.php on line 111 when visiting /index.php?m=my&f=project
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Product
17:49:49 syntax error, unexpected 'Default' (T_DEFAULT) in module/product/lang/ru.php on line 127 when visiting /index.php?m=product&f=index&locate=no
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Project
17:50:28 syntax error, unexpected 'Default' (T_DEFAULT) in module/project/lang/ru.php on line 111 when visiting /index.php?m=project&f=index&locate=no
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Test
17:51:39 syntax error, unexpected 'Default' (T_DEFAULT) in module/product/lang/ru.php on line 127 when visiting /index.php?m=qa&f=index
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Doc
17:52:02 syntax error, unexpected 'changes' (T_STRING) in module/tree/lang/ru.php on line 36 when visiting /index.php?m=doc&f=index
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Report
17:52:24 syntax error, unexpected 'Default' (T_DEFAULT) in module/product/lang/ru.php on line 127 when visiting /index.php?m=report&f=productSummary
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Company -> Dynamics
17:52:40 syntax error, unexpected 'Default' (T_DEFAULT) in module/project/lang/ru.php on line 111 when visiting /index.php?m=company&f=dynamic
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Admin -> Translate
"The translation is disabled for security reasons.To use this feature, please go to the official website to download and install the plugin of translation."
But the plugin is already installed. If we go through the English language, the plugin will be displayed.

Admin -> Home
EasyCorp Products - no icons

Perhaps there may be other errors as well.
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If we create a new language and select 简体 or 繁體 as the Reference Language, then there will be no errors, but since I do not know Chinese, it will be difficult to translate from Chinese into Russian. And there are still 2 issues:
后台 -> 翻译: 翻译功能因为安全原因被禁用。使用该功能，请到官网下载安装 翻译 插件。
后台 - > 首页: 其他产品 - still no icons

I hope there will be a solution to fix these errors. Since if I translate from English into Russian by editing the code, without translate extension, then with subsequent updates the translation will be deleted.

I also noticed that there is no way to remove the language from the admin panel.
I disabled unused languages via config.php:
// $config->langs['vi']       = 'Tiếng Việt';
// $config->langs['ja']       = '日本語';

Thanks for help.

can u send me russian lang pack too? [email protected]