The tablet navigation is wierd. But if and when you do get used to it, I guarantee at some point you'll switch from Z to Maya and start trying to navigate in Maya the same way you did in Z, without pushing the alt button, and be like...'doh'....

I didnt realise what Gubar said, that you could do it that way too...but also, aswell/instead of that....on the right side of the viewport there are scale, transform, and rotate icons, and if you click on any of them and drag then it does whichever youve chosen...thats what I always do when my model fills the screen, just click on the scale/zoom icon and drag out.

The whole, clicking on alt, and then letting go before you drag to zoom is wierd at first, but it does get easier.