[l0u0k0e] has you covered with a 3D printable focus zoom motor accessory. The motor behind it all is a geared stepper motor ... while you can write your own Arduino sketches to control it if ...

The solution is named Ethersweep, and is a small PCB stack that sits on the rear of the common NEMA17-format stepper motor ... with the Arduino software stack deployed, making uploading firmware ...