These are way different strings. I would say zm67 is better than n98, but that would be not factoring in durability. In terms of performance zm67 beats n98 in all aspects. I think their durability is close, but n98 is more durable.
Personally I prefer ZM67, for me it has better feel and at least as much power. I only tried NBG98 once though and couldn't get on with it, it just felt a bit soggy and I couldn't feel the shuttle properly. I think perhaps if I'd strung it a couple of pounds thighter it would've been better. As far as durability is concerned, I haven't been able to break ZM67 strung at 30 lbs in the last 8-9 weeks. The NBG98 I had didn't last as long - because I took a pair of scissors to it and replaced it with ZM62, which I think is even better than ZM67.
If you're going to go for ZM62, make sure you string it a couple of pounds slacker than you normally would - it's a very thin string and plays very tight. My preferred string has been BG80 at 28 lbs for ages, but I've switched to ZM62 at 26 lbs.
It feels softer than BG80 at 28 lbs and has, I think, more power & repulsion. I can generate more power from it with a hurried wrist flick than I can with BG80. I doesn't have a much grip as BG80 though, if you play a lot of sliced drops/smashes you might find it a bit slippery in comparison.
Very nice, I am waiting for the stringer to get back on the stock for ZM 62. Peter, what is the feeling for ZM67?
Finally strung the purple Ti-10 to 31 X 34 with the ZM 67 last niight and tested it! It is a very hard and tight string. It almost has no gives to it. Will test it out more later.
From the minor testing ive done on the zm62 and zm67, ive found you can string zm67 the same as you would play bg66. Zm62 needs to be about 10% less than what you would play bg66 with. Zm62 is very responsive, but is a little slippery like peter said. The bg67 does have more texture and feel if thats what you're looking for. I cant speak for zm70, .70 strings are too durable for my weak arm...
As illusionistpro says above, zm67 has more feel & texture than zm62, but not as much repulsion. I think that 67 is a more forgiving string than 62 - it seems to play well at a wider range of tensions. I found with 62, that if you string it 2 lbs too tight the sweet spot gets very small; at 2 lbs too slack it gets very bouncy on nets shots. But get it just right and it's wonderful.
I string it at 24x26 lbs on a constant pull machine with 15% prestretch, which is perfect for me. No guarantees that it'll be the same for you of course, string tension is a very personal thing...
Strung at 26 lbs, the Zymax 67 string broke during the second time I used it during a smash, not really that durable I would say