I can't stress enough the utility and usefulness of a digi-cam when working on just about anything technical. For instance: if you had used a digi-cam to do a survey of your unit before working on it and more pics as you worked on it, you wouldn't be in this situation right now.
As it is deciding where the zener goes is only a small part of the puzzle. It's orientation and the other diodes' orientation are another piece, and then, as you state, we have to find out just exactly what these parts are.
Also, I have to agree with sregor, my 56v guess was most likely wrong. 56v seems like a very high voltage for use in a pre-amp. As Hyperion guessed, 5.6v sounds much more likely. The thing is that there are usually some prefix letters in a zener string that help to identify the exact series/part. And the suffix number/letter usually identifies the tolerance class and where it falls. Such as +0/-0.5v or such. Often a zener will have a tolerance code that puts it's working range a little higher or lower than the nominal stated voltage point. This is important.
The 1000ohm pad that you found is most likely the anode pad for the zener. But that's only a guess without a schematic.
Cheers,
James