Synchronizing multiple values

I dont even know how to word this question properly, but here's the issue:

I have the scrollwheel adjust both the z distance and x rotation at the same time. I want my z distance to change from 1 to 10. but my rotation from 1 to 15. what happens is after I stop moving in z, I continue to rotate until I hit 15.. I want my rotation to hit 15 as soon as z hits 10 and both of them to hit 1 at the same time... I'm sure there's a function for it somehwere...