There are many things wrong with your Question, much detail missing.
There are 2 fundamental issues:-
735ad48f-8226-cd40-8405-77d27761a4e7 is NOT a PARTUUID
modules-load=dwc2,g_ether is incompatible with use of the USB for storage.
Frankly trying to use a Pi Zero with an external drive is a waste of time. You would be better to get a real Pi.
If you REALLY ...
Firstly you need to build the circuit described in the adafruit article that you linked. https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero/overview
Here is mine, connected to GND, GPIO12 and GPIO13:
Then in the /boot/config.txt file you need to add an overlay entry to remap the audio:
Then in 'sudo raspi-...
Look into g_multi gadget, which supports multiple functions in one configuration:
a CDC Ethernet (ECM) link
a CDC ACM (serial port) link
a USB Mass Storage device
If you want to connect your Pi to Windows, read the docs describing how to get the right drivers installed for each function.