If Joe Theismann were to rehearse in front of a giant mirror, he would see southpaw Jim Zorn of Seattle, with the reverse image of Theismann's delivery.

Zorn, like Theismann, flees the pocket at the first sight of a pass rusher's scowl. However, he doesn't do as many television commercials, doesn't operate a restaurant and did not write a book on how to quarterbck, as Theismann did when he was a third-stringer behind Sonny Jurgensen.

When they say in the great Northwest that Zorn can do it all they mean more than Theismann.Much more. He was the commencement speaker at Cal Poly (Pomona) last year, and he still hasn't graduated. He learned to play the viola in the offseason and appeared with the Seattle Symphony.

The orchestra's formation looked like a broken play because of the way he had to be positioned as a southpaw. He gave a bravura performance of "Twinkle, Twinkle, Little Star," and while the audience was still tittering at his novice effort, James Arthur Zorn moved into Beethoven's "Ode to Joy."

Joy is his wife's name.

While at liberty between engagements with the Dallas Cowboys and the Seahawks, from September 1975 to January 1976, Zorn became an amateur boxer and taught himself to be a splendid speed skater. Scouts reaching for a metaphor to describe his passing are reminded that he threw the javelin in college.

While once he ran from fright with the expansion Seahawks, the five-year veteran now has a purpose when rushers overcharge. In 1979 he ran 41 yards on a draw play designed for complacent defenses, 31 yards for a touchdown on another.

Still, he completed 56.4 percent of his passes over his first four seasons, all marked by long touchdown plays. He currently has a 57.4 percentage against defenses that know he is going to have to pass -- opponents have been completing 62 percent of their throws against the Seattle secondary.

For instance, Zorn threw four touchdown passes on Sunday and put 31 points on the scoreboard, but New England scored 37 to leave Seattle's record at 1-2. A spokesman for the Seahawks conceded, "We have a way to go on defense."

Because Zorn does not yet have a high profile in most areas of the country, the Seahawks are collecting testimony from on-the-job experts about impressions he has made.

Coach Sam Rutigliano of Cleveland on how to stop him: "Well, you could give your outside linebackers hand grenades."

Coach Bill Walsh of San Francisco: "Zorn may be single most effective player at any position in football."

Defensive tackle Mike McCoy of the Giants: "Bert Jones can't run as good as Zorn and Zorn throws as well as Jones."

Quarterback Coach Jerry Rhome of Seattle: "He runs like Steve Grogan, moves like Roger Staubach; he's got Bert Jones' accuracy; he's as smart as Bob Griese."

Defensive end Ezra Johnson of Green Bay: "We have never faced anyone as good as he is. I spent all day chasing the dude."