I and other family members have being ZX for years. It is usually very durable and we have never broken a string in the middle of the string bed. The strings have always broken at the grommet strip edge, usually on an extremely off center shot.
The red seems to be more brittle (break more easily) than the natural color. I expect the 17 to break more easily than 16. We only use 16 natural color now.
ZX is stiff sideways but stretchy in length. That results in spin and power but also brittleness.
Good qualities:
- On average, lasts three times as long as any other string we used before
- Good spin
- Lots of power (some people dont' like that)
- Very good comfort when hit in the center of the string bed
Bad qualities:
- Sensitive during stringing: needs a slow pull and careful knot
- Tension sensitive: the range of tensions that work for a particular racquet is much smaller than with most strings
- Takes a week for the tension to stabilize, then little tension loss.
- Breaks on shanks
- Poor comfort on off center hits
- Poor control if you don't center the hit. There is a big power difference between hitting the ball in the string bed center and off center. This looks like poor control on days when you hit a lot off center.