A 1/5th wave mirror isn't too bad although you can do better.
If the Zone 4 is high, do some strokes with your hands one in front of the other and push down on the one hand so that the lap works the mirror from Zone 3 to Zone 5 as you go that way. Each stroke pair (out and back) rotate the mirror by about 30 degrees and do another stoke. Two times around and test again. This should lower Zone 4 as necessary.
I'll note that this stroke will make a mirror with a TUE if you keep going at it.