[daloosaa]

Sure, that's possible!

Replace

$zhbuddy = $vbulletin->options['zh_buddy_id'];

with:

$ids_to_array = preg_split('/ /', $vbulletin->options['zh_buddy_id']);
$arraysize = count($ids_to_array) -1;
$selector = rand(0, $arraysize);
$zhbuddy = $ids_to_array[$selector];

Note: This is not tested yet (i had the same idea as you in the past 5 minutes), but should work.

EDIT:
It works - tested.