OK, so I did what I think you want to do.... Here's how:

Set Camera 1 go be a zoom camera. Go to the point in the timeline where you want the zoom to start. (In the picture, that's at 10 frames.) Slide the zoom up and release. This creates a keyframe. (Yes, you could click the keyframe icon and do the same thing, but I've always done it this way.) Reset the focal length to the focal length you are starting with. (Default is 50mm.)

Go to the point in the timeline where you want the zoom to finish (in this example that's at 2:00). Set the focal length of the camera to whatever you want. (I zoomed in using this test.)

That's it; your camera should zoom between the first keyframe you set and the second keyframe that automatically set at 2 seconds when you adjusted the focal length of the rendering camera. I clicked the tweener between 0:00 and the first keyframe and made it discrete (the little stair-step image on the timeline shows that) so the camera didn't zoom out a bit before making the zoom as it would with a bezier motion path, and I adjusted the ease in and ease out on the tweener between the focal length keyframes for a smoother start and stop.

Maybe you didn't set a starting keyframe? I can't think of another reason it wouldn't work. Hope this is helpful!

• Dex