I don't know how to make the video automatically start playing.
You will need a PHP page at the very least, and if you didn't want this in vBulletin then why did you ask about it in a general discussion
for vBulletin?
If you want to separate this from vbulletin then this is all you need in watch.php:
PHP Code:
<html>
<head>
</title>Watching Video</title>
</head>
<body>
<center>
<?PHP
$video = $_GET['video'];
echo '<object width="550" height="400"><param name="movie" value="http://www.zshare360.com/submit.api?link=http://www.zshare.net/video/'.$video.'/">
<param name="allowfullscreen" value="true">
<embed src="http://www.zshare360.com/submit.api?link=http://www.zshare.net/video/'.$video.'/" width="550" height="400" allowfullscreen="true"></embed></object>';
?>
</center>
</body>
</html>