Heart of the Swarm Campaign- Zeras Achievements: The Crucible

Normal Difficulty:

The Crucible (10): Win.

Epic Meal Time (10): Kill at least 75 enemy units with the locusts created by Kerrigan's chrysalis.  This is... not hard.  Simply using the ability frequently will net you this achievement, particularly given the preponderance of hydralisks, guardians, and zerglings in both enemy forces.

Can't Touch This Chrysalis (10): Complete the mission without the chrysalis taking any damage at all.  This is actually a bit of a challenge- the enemies interchange ground and air forces without warning and seemingly at random.  Early on, the very first wave from the East includes a number of flying enemies, and will do so continuously and in increasing number.  This makes defense on that side a bit more difficult unless you have established the secondary base for mineral gathering, in which case all the fliers from there will be diverted to your outpost rather than contributing to the main chrysalis site.  Queens and hydralisks will help with this as well, and if you're on a replay then you can ignore the Tyranozor entirely and just produce forces to defend the chrysalis and keep it intact.

Hard Difficulty:

Short Life Expectancy (10): Kill the Tyrannozor within 1 minute of its initial appearance.  This is a particular challenge in Hard difficulty, as the enemy forces clashing outside the Tyrannozor's territory will be particularly vicious towards any of your own crossing their path.  For the purpose of accomplishing this achievement, you will need to rely heavily on the chrysalis' ability to spawn locusts for defense, rather than setting up your own defenses at the ramps to the spawning pool.  You will also need to forego a certain amount of base development in the interest of quickly spawning a fast-moving assault force to take out the beast.  Mutalisks or aberrations are a must for this, as while zerglings can move in quickly enough, they are too frail when compared to the Tyrannozor's massive area-strike attack.  Be aware that there is virtually no chance your forces will dodge the conflict between the enemy broods as they head for the canyon that the Tyrannozor inhabits and thus will take some losses just getting there.  Also, having them attack-move will leave them locked up with the enemy forces en-route pretty much indefinitely- you will need to track the Tyrannozor's pacing and have them move directly into the canyon, then turn and kill off enemy forces that have followed them in, and then move to attack the beast- which means making sure they don't walk right into the end of the canyon the Tyrannozor is in, lest they be crushed by a pincer attack between it and the primal broods- which won't be attacked by or attack it.