Añadir varios países a un código en Woocommerce

// from https://elliottrichmond.co.uk/woocommerce-how-to-make-a-user-exempt-from-tax-charges/
add_filter( 'woocommerce_checkout_fields' , 'billing_company_trigger_update_checkout_on_change', 10, 1 );
function billing_company_trigger_update_checkout_on_change( $fields ) {

    $fields['billing']['billing_erers']['class'][] = 'update_totals_on_change';

    return $fields;
}

add_action( 'woocommerce_checkout_update_order_review', 'checkout_vat_exempt_based_on_billing_company', 10, 1 );
function checkout_vat_exempt_based_on_billing_company( $post_data ) {
    parse_str($post_data, $results); // Since Php 7.2, the 2nd argument is recommended in parse_str() function
    extract($results);

    $customer = WC()->customer;

    // When billing company is filled and country is Croatia: Exempt taxes
    if ( ! empty($billing_erers) && $billing_country === 'DE' && ! $customer->is_vat_exempt() ) {
        $customer->set_is_vat_exempt( true );
    }
    
    elseif ( $customer->is_vat_exempt() ){
        $customer->set_is_vat_exempt( false );
    }
}

// Cuando la empresa de facturación está llena y el país es Croacia, España o Francia: Eximir impuestos
if ( ! empty($billing_erers) && ($billing_country === 'DE' || $billing_country === 'ES' || $billing_country === 'FR') && ! $customer->is_vat_exempt() ) {
    $customer->set_is_vat_exempt( true );
}