To tell if zucchini is bad, take a look first of all at its skin; if this is dull then do not select it. To the touch, should the zucchini feel soft or mushy, then do not select it either, as it should be firm to the touch and have a live bright green color. A third way of identifying a bad zucchini is by slicing it; should the inside look dull and soft, have large seeds and stringy pulp, then the zucchini is not good to eat. Lastly, should you eat a zucchini that tastes acidic or tangy, then that is a bad zucchini and it should not be eaten.