Smaller layer height will perform a bit better. I used 0.1mm for most parts.
Print solid and you should be good! If the pin of the pupil is curling up, you can try printing at a lower temperature, increasing cooling, increasing minimum layer time, lowering layer height.
To prevent the small tabs from breaking, it helps to apply even pressure from both sides when snapping together the parts (pinch between thumb and forefinger)
With the Multipass Single Extruder Multicolor pupil, the first color is the pupil. The second color is the Outer Iris. It needs at least .5mm vertical z-hop when traveling to avoid hitting the first color and should be printed in a somewhat transparent filament. The third color is the Inner Iris. It needs 1.1mm z-hop to avoid the second color. Lower layer height = smoother gradient (I used 0.06mm). This technique may take time to perfect. Visit this video for more info
You can also just use a multicolor printer for the 3 color Iris.