Is Zelzah true stereo?

Yes, Zelzah is true stereo. It has a single TRS input jack that can receive two TS connections when using a TRS stereo adapter. Since Zelzah is true stereo, that means that there is an individual 4-Stage and 6-Stage phaser for signals processed on the left side of the pedal, and another 4-Stage and 6-Stage phaser for signals on the right side.