Hmm, just came back after a very filling meal at Zen's.
I can heartily recommend any of their omokase plates (sushi, or sashimi). Also, their grilled fish collars are excellent. See if they have hamachi or better yet, kampachi available. On occasion, they do an excellent beef tataki with the top notch triple A from Cumbrae's. If you're hungry, the futomaki has to be seen to be believed.
Other than the sushi, anything off the grill or out of the deep fryer is quite good. The only thing I would avoid the noodle soups.
Also, make sure to ask about the "kitchen specials." Some of them are excellent, like the salt-grilled squid.