Advantages:
- Adaptability: These guys can change strategy and primary units faster then any other race allowing great flexibility.
- Speed: The Zerg have the greatest production ability. They can produce units faster early game, and late game they can build a full squad of anything almost instantly. Nothing beats replacing your defense forces as fast as they can kill them.
Disadvantages:
- Defense: The zerg are somewhat weaker defensively then the other races but should not be put into a defensive position. They should always be on the move.
- Power Units: The Zerg don't really have any super units, you know like reavers! This is more then made up for by their numbers though.