The more I look at it, the more I become convinced that the Z340 needs to be transformed first before seeking its meaning, and that the ‘box corners’ are signalling how this should be done.

What is more, I’m finding it ever more likely that some of the later communications by Zodiac were intended to give clues, and that he had all of these in mind right at the time that he was putting the Z340 together, not later.

As an example, look at the box corners and how their open angle points each to a respective corner of the cipher – suggesting, to my mind, that we need to transform the ciphertext to get them there. And because of their orientation, the simplest of conceivable transformations will achieve this goal.

This, then, is what it would look like if we simply cut out the highlighted blocks and ‘rotated’ them (re-inverting the individual symbols, of course).

But is this right? Something about it seems right, just from the appearance of the box corners as internal features of the cipher.

But then what do we make of the 3-by-2 block highlighted in the next image?

Is this not reminiscent of both the ‘Peek-a-boo’ (clue?) from the Halloween card, coupled with the ‘around in the snow’ (clue?) of the Pines postcard? Is this new feature not just helping us to recognise that maybe we did something right?