Hi @veri63,
Thanks for reaching us,
In-order to access the Header Media function in the theme, you can navigate to the following two location below:
custom-header.php - wp-content\themes\zakra\inc\core
header-media.php - wp-content\themes\zakra\template-parts\hooks\header
Also, I suggest you not making any changes on the theme file. Instead create a Zakra child theme and make the changes inside the child theme as these changes will not be updated once you have updated the theme to the new version. For more information on the child theme, please check the link and work accoridngly: https://themegrill.com/blog/tutorial-creating-wordpress-child-theme/
Let me know of any confusion while doing so and I will get back to you.
Regards