Are you talking about a Custom Post Type (CPT) or a page called landing-page
?
They are completely different. See http://codex.wordpress.org/Post_Types
In any event, this will work for a custom post type or a page:
if ( !is_singular( 'custom-post-type-name-or-page-slug-here' ) ) {
get_template_part('menu');
}
It says: "If this page is not a single page or a CPT, load the file menu.php from the theme folder."
See also http://codex.wordpress.org/Include_Tags:
The get_template_part() tag includes the file {slug}.php or {slug}-{name}.php from your current theme's directory, a custom Include Tags other than header, sidebar, footer.