As zoom in / out is not an option with this app (why?) (using scrollwheel + key or mousebutton) i tried to use "CMD + and CMD -" to zoom in and out.
But using the "+" sign results in the software using the "-" sign.

Using + sign results in - output in Mac OS.

Replicate:
Try to use "+" sign with ex btn 4 + mouse move forward = Software gives a "-" sign.

Please just implement a proper zoom function in all apps using a key modifier or mousebutton.