The Equalizer in Zoom Player is pretty straight forward, but here are a few pointers to help you out:
For the Equalizer to function, the Internal Equalizer/DSP filter must be enabled (It is enabled by default).
The "Pre" (PreAmp) bar is for digital Amplification. Audio amplified digitally has a certain quality loss, using PreAmp is only
recommended if the volume on the currently playing file is really low.
When enabling the Magnetic Hard Docking button, The Equalizer will move along with the main user interface
while trying to appear on-screen in the best position (visual/space wise).