I'll not call myself an expert on this game by any extent, but I managed to pull a win with a mostly crippled Z vs. 7 opponents.
Long story short, I had altitude and better speed than all the remaining opponents (fully upgraded engines, both speed pilot skills, both speed equips, 20mm guns).
Planes could get up to my altitude and chase me, but I was able to slightly nose down in order to pick up speed and get them to 12-1300m or so before I'd do a full throttle turn and start heading back towards them. They'd pop some shots off then start to weave as I opened up, but I'd easily see the pattern and lead the shots and do 30-70 damage. A few repeats and I was down the the last fighter, a human P-51A pilot (which might have been my demise if he had gone after me) going after an IL2. I had speed, altitude, and dakka, so a pass, vertical flip, then strafe brought him down from fullish health to flames. 2 ILs later and I had run out of targets frustratingly close to a Gorovet's.
Now, this was a bit of an ideal match, but it highlights how you don't need to out-climb planes just to escape them.