Hey all, I wrote an entire guide on how to remove your bumper for the 2014+ Mazda 3 a while ago, and so used that in conjunction with a DIY video on how to Retrofit your projectors in the 2014+ halogen headlights.
Video:
https://youtu.be/VGLYGKwlck8
Disclaimer, I make cool headlights, I make mediocre videos.