ZSP-001 bought in April 2020 is not ESP8266 based (no markings on shielding can). Flashing with tuya-convert and esptool failed. They still output something via the serial console but you can’t install tasmota. For details see I opened that device and it is a Winner Micro W600 (https://w600.chip.haus) employing Arm Cortex-M3 32-bit encapsulated in an esp-12F compatible Hardware dimension despite not being https: / compatible software /docs.w600.fun/?p=product/tw-03.md This component is proposed as a more performing alternative of the esp8266 itself and already has support in Arduino.
Device is easy to open and has the four contacts for flashing similar to Sonoff devices. BUT VCC is 5v (goes through 1117-3.3v). Using the 5V pin on an FTD1232 adapter works (RX/TX are 3.3V).
Template configures red/blue LEDs and power monitoring (BL0937 chip). Calibration power monitoring is required. I got PowerSetCal:1093, VoltageSetCal:33418, CurrentSetCal:35. YMMV.