After some testing with the code I finished the project. Here's a video showing how it works (using the TJBot cardboard head as a model):

Some future improvements and lessons learned:

* Initially I wanted to control the two lens individually. Howerver, at the time I only had one servo. Since they are very lightweight, adding another servo on the other side wont increase that much the overall weight of the glass

* I was wanted to control the lights that are close to each lens, but I did not follow through. If anyone want to do that open the cases where you can replace the tiny round watch power battery and attach a cable to one of the GPIO's of the RPI Zero W. This should be an easy task but requires extra programminng to active the leds.

* I could create a better cable management and print 3D parts to accomodate the servo and the supporting ice screen stick instead of the hot glue. Maybe this will come in a next version of the prototype.

* There are alternatives for the hardware. For instance, I could replace the RPI Zero W with a tinyduino and two tinyshields: one to allow bluetooth communication with a mobile phone (which would capture the audio and do the STT)  and one to connect the tinyarduino to the servo (the Proto Board TinyShield).

* Another option I had was use a voice assistant device such as the amazon echo or GoogleHome to receive the audio. However, this approach may have some issues when doctors use masks on their faces. I tested this scenarion with the USB microphone connected with the RPI Zero W and have no problem to understand the two commands (up and dow).