Filter the ZeroBounce status before an API call is made to add your own validation logic.

filter-zb-status.php

<?php

add_filter( 'groundhogg/zerobounce/zb_status', 'filter_zb_status', 10, 2 );

/**
 * Filter the status
 * 
 * @param string|false $status
 * @param \Groundhogg\Contact $contact
 *                                    
 * @return string
 */
function filter_zb_status( $status, $contact ){
	
	// The provided status is valid
	if ( \GroundhoggZeroBounce\is_zb_status($status) ){
		return $status;
	}
	
	$email = $contact->get_email();
	
	// Check the email in someway
	if ( str_ends_with( $email, '@gmail.com' ) ){
		return 'valid';
	}
	
	// Returning false will force an API call to validate the email address
	return false;
}