Using NS Name Split with HikaShop is possible but it requries some modifications due to both plugins using the same save function when writing names to the database.

1. In nsnamesplit.php add this new code right after the UPDATE users script

$q= "INSERT INTO #__hikashop_user (user_cms_id, user_email) ";
$q .= "VALUES (".(int)$user['id'].", '".$db->getEscaped($user['email'])."') ";
$db->setQuery($q);
$db->query();

2. In hikashopuser.php (plugins/system/hikashopuser/hikashopuser.php) comment out lines 25/26 which is the function onUserAfterSave

It should look like:

/*function onUserAfterSave($user, $isnew, $success, $msg){
return $this->onAfterStoreUser($user, $isnew, $success, $msg);
}*/