Instead of simply describing a zebra, the poem tries to make one happen on the page. The opening image is of black-and-white stripes blurring as the animal runs, and the movement quickly becomes sound: the pounding hooves turn into a "fluctuating bassline," a beat you can almost feel in your chest. Even the title works like a command, turning "zebra" into something you do to a piece of writing.
In the second half, the energy folds back in on itself. The sound rises from the sand, echoes, and returns to its source, filling an "would-be hollow" with the strength left over from the run. I read that as the zebra, or the poem, powering itself, so that the effort doesn't drain it but refuels it. The speaker stays mostly out of sight, more observer than character. The mood is fast, rhythmic and a little hypnotic, with a sense of admiration for something that sustains itself through its own motion.