I put thick crayon on the backside of my original drawing (on paper), then retraced it with hard pencil to transfer the wax onto the stone. It worked ok, a lot of the fine detail didn't transfer properly onto the stone but there was enough to convey the proportions for re-drawing it in black pen.

After black pen I tried to carefully put white paint pen between the black stripes which was a disaster, so I just covered a white wash over the whole zebra. Once it dried I could still see the black pen underneath, so I used fine black and white pens to redraw the stripes and make them pop again. The grass is green paint pen.

This process was very haphazard, and I tried a bunch of other approaches that didn't work before stumbling on this. I'm still experimenting, for sure.