Oh, there's so much you can do! You've gotten some good suggestions already.
Part of the zooming is, like you've pointed out, a young dog lacking physical exercise. Part is stress. Now I know some people will disagree and say "But Princess looks so happy", well yes, some dogs stress up, some stress down. If you'd rather call stressing up, over-excitement, that's fine. But think of asking a kid to do geometry right before they open their presents on Christmas morning. It's hard to calm down enough to do that. Rescue Remedy may help some of this.
Join the sighthound agility list. search yahoo groups under SHagility list.
Work through Control Unleashed excercises. There is a book and 2 sets of DVD's. Pay close attention to mat work, Gimme A Break, whiplash turn, look at that and box work. (off the top of my head) You can do these on your own, but if you can find a local CU class, that'd be awesome. There weren't any classes in my area when i felt like a needed to be doing these things with Zest, so i ended up teaching my own class. One of my students with a Rhodesian Ridgie, told me she could yell "MAT!" as her dog began to zoom in class, and her dog would run to the mat and down. It does take a while to get to that point, which brings us to:
http://dogscouts.org/Protocol_for_relaxation.html
I use a down instead of a sit, but these steps made doing a lead out with Zest a snap! I also started teaching front crosses with her on her mat and got her used to me going behind her with out a spin. Very handy in agility.
Also, have you done any foundation work without the obstacles? I'm think of Greg Derrett type stuff where you run around in spirals and figure 8's with the dog moving beside you? That's really the place to start running a course. You can find GD's dvd's at cleanrun.com or dogwise. it's a little pricey, so you many want to see if you can rent/borrow his foundations dvd from somewhere. I know cleanrun does some of that and there is an educational dvd rental place somewhere on line. i do not know if they have that particular video.
Additionally, i would purchase the Jan 2011 issue of Cleanrun. It's the one with the pretty samoyed on the cover. there is a GREAT article on focus written by someone who has/trains/runs terriers and a whippet. She's also on the SHAgility list.