To make this Starcraft 2 guide effective against Zerg enemies, your highest priority should be taking down their Hatchery as they will try to bring out an Overseer when you attack them with Dark Templars. If you are able to sneak into their base without being noticed, 4 Dark Templars are usually enough to take down a Lair before an Overseer is produced.
Do note that Dark Templars alone cannot hope to defeat a Zerg player as it is extremely easy for them to obtain an Overseer (detector). However, f you take them by surprise you can kill many Drones and even a Hatchery.
