Thank you Eliseat
I am starting to catch up with all the video processing.
Thanks for the link to that thread. It is exactly the problem I have.
I was using the preset "Basic helpers: Track/opacity/zoom/pan" and in RGB colorspace in project settings. Now I changed to YUY2 or to I420/YV12 and it zooms much smoother. I'll keep investigating. So far changing &-2 to $-1 as Justin said in that thread doesn't seem to help in RGB colorspace. I'll just use YUY2 for now
edit: I was testing on a new project and it seemed ok with a normal image. back with the project with the problem which has larger images, larger than the project resolution, and it is not smooth movement/zooming. I need to work with large images to zoom in. So this may not work... I really wanted to generate the video in REAPER