Most of the time it isn't horrible, because, lets face it. Anyone who would study the golf swing enough to even try a zero shift swing, obviously spends some time on their game.
I really don't know what your getting at. If a zero shift works for you...great, do it. In general, I am not a fan of the Turned Shoulder Plane at impact, and think it looks rather silly to set up with the hands on the TSP. Now that is not to say the TSP is invalid or shouldn't be taught. But when speaking of a zero shift, that means setup, backswing & downswing all on the TSP, no exceptions. Most golfers don't do that...most good golfers set up on the hands only plane, so a shift has to happen.
The above is my problem with a so called zero shift...it is simply really hard to do...and don't tell me you can zero shift on the elbow plane for any thing longer than a 1/2 shot.
The TSP is valid and tons of great ball strikers are on that plane...I just prefer the standard double shift and returning to the elbow plane to hit the ball