I did it! With a little help from Jim the gardener (who used to be a physics teacher).
I used the closest to ideal resitors I could find. 4 x 54's and 1 x 120 gave me about 11 dB of attenuation.
I built an H-type balanced circuit on a piece of circuit board and inserted it at the Male end of the XLR. I then made a loop in that end of the XLR and cable tied the circuit into the loop so as to keep the joint as safe as possible.
It did the job well and I proceeded to make a good recording. If I hadn't built this pad in to the cable then the recording could quite easily have been a distorted one.
Thanks to everyone for their pointers.
Remember everyone: Sennheiser ME66 Mics are to hot for the Sony Z1. The Z1 just doesn't have the dynamic range.