Hi
You can control the duration of the Zoom effect by altering the time between the start point and the end point of the effect. Obviously the effect can last no longer than the length of the clip it is applied to.
Video clips cannot be made longer so for a particular clip the zoom speed cannot be slowed down (decreased) more than than this duration. If you want a slower zoom then you would need to make the clip longer either by shooting a longer clip in the first place or by changing the speed of the clip so it lasts longer. (Setting values of less than 100%)
If you use an Image clip then the duration, which is set by default in Options/Media , can be made effectively as long as you like although this value will be global for all image clips. If you don't want to reset the default value you can simple drag the end of the Image clip along the timeline to the right or use Storyboard mode to enter a specific value for the clip in question..
The start and finish points for the zoom effect in a clip are, (or can be) set by using keyframes, the zoom level being set for each keyframe. The shorter the interval between start and end the faster the zoom.
Pan and Zoom act on the whole clip and consists of setting the first frame position in clip preview and then the final zoom position in clip preview. As mentioned the speed will depend on the duration of the clip. The longer the clip, the slower the zoom/pan.
Once you have set a zoom effect that you like and are going to use repeatedly it can be saved to the effects list by clicking the blue cassette tab and providing a suitable name. Once this has been done your new zoom effect can be added to your clips like any other effect.
Nat