When I got Buddy he wasn't flying. I realized a few things early on. He had to learn to fly & he was malnurished (seed diet). My Dad kept him "in feet" from the front door & was clipped young. I got the diet fixed, started excersising his legs. Then onto flying. It too time patience & some creativity but between my husband & I we got him to go. However that all being said my 1st vet clipped him when I was asking about it... Buddy launched & spazzily flew thru the house, panicked & flew hard into a wall. So hard he bruised his beak. Luckily it did no other damage. That clipping made a new life & new to flying, very uncoordinated. I hope he never needs it for health issues...
Now, that being said, he's around 27 (young for a Zon), Atrophy & some kind of bone growth in his wings causes him pain. He tells me in his own way, as a good day to fly or not. A good indicator also is my arthritis, if I hurt, he really hurts, I don't make him. He now flys when he wants, or occasionally when commanded, or when vaccuuming is happening near his cage. I'm happy he's able to live a bird life finally (being in captivity) I love my floof & he shows me every day, how he loves me. I know for that it's worth all the noise, extra work & $ to keep him fed, chewing & healthy.
I'm only a fan of clipping when it's a health issue to that bird or if a bird is divebombing other birds or kids. There can be exceptions to this fan based comment but I haven't found many acceptable to the inner me yet.