The wording is not the best.
ZR is "151 MPH +" It's the plus that matters. It should read 151-265.
The DOT Z rating is 149+. That's pretty wide open. Does that mean that 600 mph is ok? The R after the Z means it is a radial construction and has nothing to do with the speed.
The "200 MPH +" listing is only a guide that tells you that it's important to remove mass at higher speeds, and as John noted, not always necessary.
"265 MPH +" Above 265 you need "LSR or other racing tires".
The DOT speed rating for V is 149. SCTA will allow a V rated tire in the 130 to 150 range, and allow it up to 200 if it is shaved.
What is shaved? Since there is no guideline or dimensions it is something between taking anything off, which technically could be called shaved, up to just short of the cords showing through, and that would be the maximum mass you could remove, and close to the preferred shaved dimension.
