Help with Reverse Engineering simple Audio PCB - ESD Protection and Filter

[NNeerr00]

Hi everyone,

I’m pretty new to PCB design and reverse engineering, and this is my first attempt at trying to reverse engineer a part of a PCB. So far, I’ve managed to trace out a portion of the schematic (see attached picture and schematic), but I could use some help moving forward.

What I’ve found:
    - The section seems to be a filter circuit with an L-C combination.
    - Component SX603 looks like it might be an ESD protection diode.

My questions:
How can I figure out the values for:
    - C600, L600, C601, L601, and SX603?
    - What’s the purpose of the 0-ohm resistor in the circuit? I’m seeing one here, but I’m not sure why it's used.
    - Why is the ESD diode only placed on the tip and not also on the ring of the connector? Is there a design reason behind this?

Any advice or guidance would be greatly appreciated, especially since this is my first time trying something like this. Thanks in advance for your help!