Not surprisingly, I have two--the original Mark 1 I built from the old BYOC Overdrive kit, and a Mark II (S/N 029) that I threw in for myself during a run of customer builds. I have a special little adapter board in it that I got from Monte Allums that let's me run two op amps simultaneously, and for clipping, I have the BS170 MOSFET pair on one side and a single BS170 on the other side. This latter is an interesting concept I read about on Jack Orman's site in THIS ARTICLE. To quote Jack directly:

"An alternate method is to use on a single mosfet. With this clipper, the positive voltages are clipped by the gate-source diode and the negative voltages are limited by the body diode. This version gives asymmetrical clipping that tends to emphasis the even harmonics.

If the gate-source threshold is 2v and the body diode is 0.7v then the signal will be able to swing only +2v and -0.7v. Try this setup for a different and unique sound. "

It's a little louder and cleaner than the dual MOSFET clippers, and has a real pleasing character to it. I have that first clipping position set up with sockets so that I can change the clippers as the whim strikes me. Another diode combo I really like is one 1N914 silicon diode on one side and three 914's in series (in the opposite polarity direction, of course) on the other side.

My thanks to all of you who purchased ZYS's over the 4 years I was selling them. In total, I sold about 70 of them before I decided to stop building commercially, by far my most popular pedal. A lot of the credit has to go to Robert and his excellent ZYS demo videos. A major portion of the gear I have was purchased with the proceeds from those pedal sales.