Here is the full list of all 40 Zolg achievements.
Kill a quad shooter.
Get at least 1 health powerup.
Kill a crawler.
Get the charge shot powerup.
Kill the first boss.
Kill the first boss without getting hit.
Kill an orbital.
Kill a bouncer.
Complete the game with only 3 health.
Complete the game with 4 or less health.
Complete the game with 5 or less health.
Complete the game with 6 or less health.
Complete the game with 7 or less health.
Complete the game with 800 or less shots fired.
Complete the game with 1200 or less shots fired.
Complete the game with 1500 or less shots fired.
Kill a stalker.
Kill a defender.
Complete the game with 20 or less deaths.
Complete the game with 5 or less deaths.
Get the strength boost powerup.
Get the speed boost powerup.
Get the shield powerup.
Get at least 2 health powerups.
Get at least 3 health powerups.
Get at least 4 health powerups.
Get all 5 health powerups.
Complete the game in 60 or less minutes.
Complete the game in 40 or less minutes.
Complete the game in 20 or less minutes.
Kill the second boss.
Kill the third boss.
Kill the fourth boss.
Kill the fifth boss.
Kill the final boss.
Kill the second boss without getting hit.
Kill the third boss without getting hit.
Kill the fourth boss without getting hit.
Kill the fifth boss without getting hit.
Kill the final boss without getting hit.