To slice zucchini into rounds, first cut off the blossom end and the stem end. Hold one end of the zucchini in place with your hand. Then cut it into rounds of the desired thickness, by keeping the tip of the knife resting on the cutting board, and using a rocking motion with the other end of the knife. Keep the knife in one place on the board and push the zucchini toward the knife.
To slice zucchini into strips, first cut off the blossom end and the stem end. Then cut the zucchini lengthwise into to 3 or 4 strips.
To dice the zucchini, cut the stack of strips lengthwise down the middle, turn the strips sideways, and then cut them into small cubes.