Arduino is an open-source hardware and sofware platform based on easy-to-use electronics and code.
An Arduino Uno is an excellent option to drive your SMARS. The SMARS case was specifically designed for the Arduino UNO (or clone). Official Arduinos are more expensive than Raspberry Pi Zero WH's and are only 8 bit but there is a wide range of open source code available, and they have plenty of IO pins.
The Arduino pictured above is the Arduino Uno, its powered by an 8 bit chip, the ATMEGA328P, designed by ATMEL. Arduino is programmed using the Arduino Integrated Development Environment (IDE), which enables you quickly create code, compile it and upload it to the board.
The Arduino has 19 Pins - 13 Digital, and 6 Analog pins.