WooCommerce Visual Hook Guide: Single Product Page

<?php echo do_shortcode( '[ecp code="vtigerwebform"]' ); ?>

# Edit the functions.php in your wordpress theme folder.

add_action( 'woocommerce_after_single_product' , 'shortcode_vtigerwebform', 5 );
 
function shortcode_vtigerwebform() {
    echo do_shortcode( '[ecp code="vtigerwebform"]' );
}

https://businessbloomer.com/woocommerce-visual-hook-guide-single-product-page/

https://businessbloomer.com/woocommerce-add-content-below-the-single-product-page-images/

https://www.000webhost.com/blog/wordpress-do_shortcode/

https://wordpress.org/plugins/easy-code-placement/