This is something that used to be mentioned by camera magazines back in the 1970s. I don't know that there is any fix, because on one hand, you one "one-touch" zooms (lenses that allow zooming and focusing with one ring) to be loose enough that you can zoom easily and quickly. On the other hand, if your camera isn't level, you don't want the focal length to change.
I have a two Vivitar Series 1 zooms. One creeps. The other doesn't. I also have a Pentax "M" zoom, which focuses very smoothly but requires way too much effort to push and pull to change focal length.
Frankly, I don't know the answer, because anything that you would use to prevent creep will also get in the way when you try to zoom.
Perhaps, that are some grub screws in the barrel that can be tightened or loosened. I've never really investigated this. You probably would have to adjust these screws very carefully.