Conflct with Plugin "Onyx Files"

What’s wrong?
Editing sample galleries or creating a new gallery in admin area shows only an empty page.
Using the ini-Setting ‘display_errors’ in Plugin’s index.php and repeating the actions shows that plugin crashes with a fatal error.

Error Message
Fatal error: Cannot redeclare create_zip() (previously declared in /…hidden…/wp-content/plugins/onyxfiles/inc/helpers/func.inc.php:190) in /…hidden…/wp-content/plugins/contest-gallery/admin/gallery/get-data.php on line 411
Urgently recommending to use ‘function_exists(‘funcname’)’ or much more better to use namespaces and full qualified function-/method-/classnames.

Please fis this Bug/Error asap. Thanks.

Also recommended:
to use PSR-1 coding standards, if not already used
https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-1-basic-coding-standard.md