I know if you press + or - will zoom out and in a zbrush doc. However, i saw this video where the guy was zooming in without using these keys, he was zooming just by dragging his mouse or pressing some button. What I don’t like about using the + and - keys are they snap zoom an object if you know what i mean. I want to be able to zoom in an object like how it is in regular 3d modeling packages. I basically want to dolly in using the drag of a mouse, basically a smooth zoom in and out. Are there any ways to do this?
There’s a series of buttons lined down the right side of your screen -one of them says zoom - click and hold it while dragging down to zoom in and drag up to zoom out. But if you do it this way, the closer you zoom in the more jagged your edges get. Another way to do it without getting jagged edges is to use the scale button - works the same way -click and drag up or down. If you use the zoom and want to go back to your original size, just click actual. If you use scale and want to go back to your original size, click move.
Hold ALT+Left mouse button to drag the model.
Hold ALT, press Left mouse button and then release it (while holding ALT pressed) to zoom.
…after three try it’s very easy 
Pilou
Man. Many thanks. I’ve been scratching my head and fiddling non stop with the keys of how I accidentally came across this function, but could neve get it to work. So it’s the sequence of buttons in use. Thanks.
Unfortunately it’s the opposite of what cubik wrote:
Press Alt, left-click and then release Alt and move the mouse or pen up or downwards.
Cubik,thank you
:*