I brought out wires from the PP22 and PP23 USB pads on the rear side of Pi Zero W to an external connector. Also, took out wires from PP1 (5V) and PP6 (GND) for providing power to Pi Zero externally. During the process, I am sure that I did not short either of the USB wires to those coming from PP1 or PP6.
When I switched on the Pi, it booted up normally, but the mouse that I connected to its USB port did not work. Then, I measured the voltage between the PP1 (5V) and the micro USB connector body and found it to be 5V. So, it is getting the power but data lines are not working.
Any idea how to fix this?