Add this code into function.php of your child theme.

Please make all changes to the child theme files, and do not add the code directly to the theme files, otherwise after updating the theme your fixes will be lost

function.php

// ------------------------------------------------------
//         Groovy Menu plugin integration
//                for Zephyr ver.7+
// ------------------------------------------------------
if ( ! function_exists( 'gm_child_show_groovy_menu' ) ) {
	function gm_child_show_groovy_menu() {
		// Work only if Groovy Menu plugin active.
		if ( function_exists( 'groovy_menu' ) ) {

			// Override global variable for hidden header.
			global $us_header_settings;
			$us_header_settings['is_hidden'] = true;

			// Output Groovy Menu.
			groovy_menu();
		}
	}
}

// Add action for early BODY start.
add_action( 'us_before_canvas', 'gm_child_show_groovy_menu', 5 );
Note: You can find the child theme for the Zephyr Theme in the Groovy Menu > Integration section