mmh well sorry, it's not about the rotation focus. In perspective, the zoom is relative to the size of the object when you press z so the the move is coherent, hence if you focus on a big object and then try to zoom on a little object right after, it will be "slow" because the zooming ratio is still adapted to the big…
At the bottom right of 3D Max there is an Orbit button. Click and hold on that button, then select the bottom option, Orbit SubObject. This will help with the "fast rotation". Once you set it the Alt+Middle Mouse drag becomes slightly different. Instead of orbiting around the object you have selected it'll use the…