What was the SG? It might be finished, and very dry. If less than 1.000, I would add sorbate to stabilize, then you can add sugar in little steps until it comes to you're liking. Then, again test the SG, so you know (about) where you like it. Different fruits will turn out higher or lower. I have never made one, but I expect that a zucchini wine would need more back-sweetening. I could be wrong though.
BTW, my friend makes a strawberry-rhubarb wine that is 'to die for'!
BTW, my friend makes a strawberry-rhubarb wine that is 'to die for'!