This trailer was just released in Korea and features multiple Zerg units. To name only few they are none other than, Ultralisks, zerglings and the "marine slayers" Lurkers. Also we can see that zergs will still be a race that is focused to have enormously large armies.
The second video which is originally provided by thisisgame.com, features 9 minutes of gameplay with Zerg.
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The zerg are coming, the zerg are coming..

The long awaited trailer from Blizzard about the Zerg race for the upcoming Starcraft sequel - Starcraft II, has finally been revealed.
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http://www.teamliquid.net/forum/viewmessage.php?topic_id=67764
Anyways, the zerg look awesome!
The graphics is awesome but I am afraid the gameplay will suffer from it.