I also have a zowie am and roccat savu, both optical sensors and both fail hugely on my qck heavy. Terrible skipping and malfunctions. Can't make quick moves (play with very low sensitivity and 400-450 dpi and 500 hz)
Until i ordered an Artisan Hien Mid Large size.
Simply the best mousepad i have ever had (comiung from razer control and speed editions, ss 9hd, roccat taito-the most terrible of all and ss qck heavy)
Unique surface, although i have sweaty hands, i dont skip not one tiny bit. My aim in cod4 has been improved so much i cannot believe it.
Either way, use that guide
to force your zowie to 500 hz, because even if you put it to 500 hz, you will notice few 1000 hz rates in mouserate checker.