function display_mailchimp_rss_feed() {
    // Replace with your Mailchimp RSS URL
    $rss_url = 'https://us4.campaign-archive.com/feed?u=9dfbdb07412058c79f18b5787&id=540ff8c0bd';
    
    // Include WordPress RSS functions
    include_once(ABSPATH . WPINC . '/feed.php');
    
    // Fetch the feed
    $rss = fetch_feed($rss_url);
    
    // Check for errors
    if (is_wp_error($rss)) {
        return '<div class="rss-error">Error loading RSS feed: ' . $rss->get_error_message() . '</div>';
    }
    
    // Get up to 5 items
    $max_items = $rss->get_item_quantity(5);
    $rss_items = $rss->get_items(0, $max_items);
    
    // Start output
    $output = '<ul class="mailchimp-rss-feed">';
    foreach ($rss_items as $item) {
        $output .= '<li>';
        $output .= '<a href="' . esc_url($item->get_permalink()) . '" target="_blank">';
        $output .= esc_html($item->get_title());
        $output .= '</a>';
        $output .= '<div class="rss-date">' . $item->get_date('F j, Y') . '</div>';
        $output .= '</li>';
    }
    $output .= '</ul>';
    
    return $output;
}
add_shortcode('mailchimp_rss', 'display_mailchimp_rss_feed');

https://us4.campaign-archive.com/feed?u=9dfbdb07412058c79f18b5787&id=540ff8c0bd