If you somehow encounter a Quetzal on the ground and you can't fly up there to shoot at it, forget it. It's impossible to shoot at it from the ground it doesn't hit the Quetzal. Just get a flyer like the PTERANODON, GRIFFIN, or TAPIJARA, and you should be fine.
So... I figured out the exact spots for the spawns 👍 The primary spot is just behind the red obelisk on the thin little strip of land near the southern island. (I almost always see one spawn there) I also find them frequently spawning around the “back spike” of the red obelisk. You will almost always find a quetz around these two places. (At least on mobile) If you want a high level, just kill the one that spawns at these two places and a new one will always respawn back at those two places. This technique worked for me.
I’m a lvl 84 and I’ve only seen these guys about 7 times. I was on my Argy, higher than the tallest redwood tree and I seen them. Yes they like to fly high and they have been watching you tame that lvl 45 dilo.