Mở file functions.php trong child theme của bạn (nếu chưa có child theme, bạn nên tạo child theme để tránh mất thay đổi khi update theme). Thêm đoạn code sau:

//Chia sẻ bài viết lên mạng xã hội
function custom_social_share_buttons($content) {
if (is_single() || is_page()) {
$url = urlencode(get_permalink());
$title = urlencode(get_the_title());

$facebook = "https://www.facebook.com/sharer/sharer.php?u=$url";
$twitter = "https://x.com/intent/tweet?text=$title&url=$url";
$pinterest = "https://pinterest.com/pin/create/button/?url=$url&description=$title";
$messenger_web = "https://www.messenger.com/share?link=$url";
$messenger_mobile = "fb-messenger://share?link=$url";

$html = '<style>
.custom-social-share {
display: flex;
align-items: center;
gap: 10px;
}
.custom-social-share p {
margin: 0;
font-weight: bold;
}
.social-btn, .copy-link {
font-size: 1em;
text-decoration: none;
border: none;
background: none;
cursor: pointer;
}
.zalo-share-button {

transform-origin: center;
}
.copy-link {
position: relative;
top: 6px;
}
</style>';

$html .= '<div class="custom-social-share">';
$html .= '<p>Chia sẻ bài viết:</p>';
$html .= '<a href="' . $facebook . '" target="_blank" class="social-btn fb"><i class="fab fa-facebook-f"></i></a>';
$html .= '<a href="' . $twitter . '" target="_blank" class="social-btn x"><i class="fab fa-twitter"></i></a>';
$html .= '<a href="' . $pinterest . '" target="_blank" class="social-btn pin"><i class="fab fa-pinterest"></i></a>';
$html .= '<div class="zalo-share-button" data-href="' . get_permalink() . '" data-oaid="43280336123456" data-layout="1" data-color="blue" data-customize="false"></div>';
$html .= '<a href="' . $messenger_web . '" target="_blank" class="social-btn msg" onclick="openMessenger(event)"><i class="fab fa-facebook-messenger"></i></a>';
$html .= '<button class="copy-link" onclick="copyLink()"><i class="fas fa-link"></i></button>';
$html .= '</div>';

$html .= '<script src="https://sp.zalo.me/plugins/sdk.js"></script>';
$html .= '<script>
function copyLink() {
navigator.clipboard.writeText("' . get_permalink() . '");
alert("Link đã được copy!");
}
function openMessenger(event) {
event.preventDefault();
var isMobile = /iPhone|iPad|iPod|Android/i.test(navigator.userAgent);
var url = isMobile ? "' . $messenger_mobile . '" : "' . $messenger_web . '";
window.open(url, "_blank");
}
</script>';

return $content . $html;
}
return $content;
}
add_filter('the_content', 'custom_social_share_buttons');

Thay data-oaid=”43280336123456″ bằng OA ID của bạn. Lấy tại https://developers.zalo.me/docs/social/share