What are you turning? The zoom ring or the focus ring? Your first contact for such questions is the Service Center of your lens maker .. what is it, actually? A more speaking thread title would also be beneficial to other people so that they can see in one line what your thread is about.
Actually, I wanna give a shot answering TS. Give it a try and point ur lens downwards then zoom in, does it still feels tight, then point the lens upwards and do the same again, do u feel the tightness again?
If it's no then yes, then it's normal. Super zoom lens tend to have this issue. Use gravity to zoom will help.