The default is to have servers sorted by id, so put your 3 servers in the top of the list. Use the advanced button if you want to easily re-arrange your list.
To make it do <br /> after 3 servers, change:
foreach ($server_list as $server)
{
To
foreach ($server_list as $key => $server)
{
if ($key == 3) { $output .= "<br /><br />";
To do something based on the zone:
if ($server['o']['zone'] == 3)
{
$output .= "do something";