Hello, you cna do it with one event
Set the Layout Scale by system action to this kind of formula :
LayoutScale = LayoutScale+(DesiredScale-LayoutScale)/Factor
Factor modulate speed at which the new scale is reached. Try 10 and change as you wish.
LayoutScale is 1 for default zoom, 2 for zoomed twice, 0.5 for dezoomed, and everything in between.
Set the LayoutScale everytick or x seconds when you're zooming. This function increments fast when far away from targeted value, and will slow down when closing.
OR you can use the Magicam plugin for Construct 2, it has an action for smoothly zooming to a defined scale.