What is the minimum distant for Zu?

All rooms are different. It is my experience that all speakers end up sounding the best in the same location in a given room. If you used speakers in this room before and found the optimum location that is where these speakers should be. If not, it is trial and error until you find it.

Morganc, All speakers need the same attention as your Zu speakers, but once you learn your room you will find other speakers will sound their best in the same place as the Zu.

Onhwy61, You are right about the listening position being fixed. I have experienced this in the last three homes I have lived in with a variety of speakers from Martin Logan full range electrstatics, Magnepan, Vandersteen and Dunlavy to smaller speakers from Green Mountain Audio, Von Schweikert and Revel. All of these speakers performed their best in the same location. There will always be minor adjustments, but the room plays a bigger part in the overall sound than most people realize.