The MZ-2 is a somewhat unusual distortion pedal as it has 3 doubling modes, 2 chorus modes as well as a normal distortion mode. The distortion is produced in an analog circuit while the chorus and delay functions are created using a digital chip. The pedal has 2 main circuit boards where one of them is analog and the other one digital. The MZ-2 has stereo outputs which is unusual for a distortion pedal but makes perfect sense because of the doubling modes.

The MZ-2 has 6 different modes:
Straight distortion
Distortion/delay (3 modes)
Distortion/chorus (2 modes)

The MZ-2 remained unchanged throughout its 4 year life time. Production came to an end some time 1991 but the pedal was still marketed for another year.

Specifications
Controls: Level, Tone, Drive, 6-way Mode switch
Connectors: Input, Output A, Output B, AC Adaptor
Current Draw: 70 mA (DC 9V)
Weight: 450g/0.99 lbs.
Input Impedance: 1Mohm
Equivalent Input Noise: -120 dBm (IHF-A)
Recommended Load Impedance: 10kOhm or greater
Recommended AC Adaptor: PSA Series

Labels
Blue – Made In Japan
The MZ-2 was sold from December 1987 to August 1992.

https://www.stompbx.com/pedals/boss-mz-2-digital-metalizer