Good question. I would like to know as well. I'm starting to get to the point where I can do a fairly steady zoom with my 45 to 200 lens but the 14 to 42 sticks way too much for a nice slow zoom.
I know older manual lenses will be much smoother. I have a couple of Canon Fd lenses that focus and zoom like butter but they weigh a ton so are virtually impossible to use without a good tripod.