Compared Zg7 to Scythe, Og65 and OG30 this am. I was shooting an 18" .223AI bolt action. Sound wise, ZG was noticeable the quietest. I could literally here the firing pin drop. Scythe was next, followed pretty close by the OG65 and a ways off was the OG30.
Mirage- All were shot with LS wild covers on. ZG7, Scythe and OG65 were almost identical in mirage for me. All started to show mirage around shot 6 but not enough to affect shooting 10 shot strings. OG30 had almost no mirage at shot 10.
ZG7 surpasses expectations by a wide margin. I bought this for a 6.5PRC build, but while I wait for that barrel to arrive, I think it will live on a 22CM.