Not bad. But it does not entirely flash me. There is a lot of shading missing, the blood seems weird considering he is a robot and also all these grey areas indicating dust (i guess) are flat thrown all over the place - ignoring edges of R2D2 as well as of the blood, which seems to be fluid and thus shouldn't be affected the same way as a solid surface.
However, the main thing to add is: If you want to enter the Challenge, you need to tag it "cotm_zombie" because he will just search for this single tag.
Besides, it is an ok work and even though Jazza said it has to be something that can become a zombie (and robots can't because they are not alive), i don't think he will be this strict.