code to delete user data from custom table.

wp_delete_user.php

function zi_delete_user( $user_id ) 
{
    global $wpdb;
    // get user details base on  user id
    $user_obj = get_userdata( $user_id );

    // Array of all tables
    $tables = array('wp_zi_answer', 'wp_zi_answer_interventions_basic', 'wp_zi_daily_answer', 'wp_zi_goal_basic', 'wp_zi_lifestyle_answer', 'wp_zi_setting');
    
    foreach($tables as $table)
    {
        // Delete all data have deleted user id
	      $query_zi_table = $wpdb->query("DELETE FROM `user_id` where `user_id` = ".$user_obj->ID."");
    }
}
add_action( 'delete_user', 'zi_delete_user' );