Use OnlineMapsControlBase.OnValidateZoom to modify the rules for a particular zoom type.
As an example, use SmoothZoomOnMouseEvents script.
If zoomEvent == OnlineMapsZoomEvent.gesture, calculate the desired floatZoom, set it and cancel the zoom event (return false).

Hi,

I would like to change the amount of zoom done when the user use pinch to zoom to zoom on a mobile device. I've been checking the code but I can´t find where I could change it.

Let me explain, imagine that now the zoom multiplier is about 1x, so I want it to be something like 2,5x.

I'm using the V3 version of Online Maps with smooth zoom enabled.

Thanks in advance.