[PROBLEM] Audio glitches (dropouts, clicks and pops) using USB DAC plugged to Pi Zero W

[DRONE7]

I had my Pi plugged into a Anker Power 20.000mAh Powerbank.

I'm now powering it with the power supply that came directly with the Pi, I'm hearing less drop-outs, but not zero dropouts!

The DAC is a powered directly from the Pi. I've read that the micro-USB on the Pi Zero is directly hooked to the power in, so it shouldn't have any issues powering this small dongle that should draw 100mA top..

Note the conflict here...   You improved the power-supply and things improved but you don't feel that trying further supply experiments will improve things further.

OK, other things to try would be another Pi.    The  Zero is limited in CPU count and ram. 
The DAC is usually recommended for Phone use and they have much more ram and cpu than the Zero.
A Pi 3b idles along at around 5-10% cpu use.
Where are the files you are playing stored ?  Network performance ?