I have looked at BD's z-poles, and they appear to be the most compromised design that the company has ever made for trekking use. They are highly optimised for a very niche market - mountaineers and mountain runners. BD has clearly identified that this niche is prepared to compromise on the overall flexibility of the more traditional design to get a light pole that is very compact when collapsed.
The compromises that I see are
- no or very little adjustment - max of 20 cm of adjustment on those models that do. None on the ones that don't. A good range of adjustment is required on steeper descents in particular to ensure that you can reach further ahead of your feet without leaning too far forward. This provides greater stability during longer steeper descents.
- Sherpas bend over because they are so heavily loaded that this is the only way they can get their overall centre of gravity over their feet. Skiers do too because they are interested in speed, and want to both decrease their frontal surface area and use their ski poles to give maximum forward propulsion. These should be quite different to the demands of the camino.
- my experience is that if your pack balance is good, you should not need to lean much, if any, further forward going downhills, even on quite steep slopes. While I don't expect that you would have to extend poles this far on the camino, I have negotiated slopes on St Olavs Way in Norway where I had fully extended the top section from 110 cm to 140 cm. Any fixed length pole is a real compromise in those conditions, and a 20 cm extension still not ideal.
- the grips and strap appear to be minimalist designs compared to many of the other grips and strap arrangements on other models in the BD range. In my view, the quality of the hand grip is somewhat less important, as one shouldn't be grasping it when using the pole. But this relies on having a decent strap arrangement, and z-poles appear to me to fail in both areas when I have tried them.
- the use of a non-standard tip arrangement which only has two tips, and you are tied to the BD proprietary replacements. Unlike other carbide tips that have a 12 mm diameter and can accept replacement rubber tips from other makers and use specialised walking and nordic walking tips, it appears that with z-poles, you get only two types, and get and replacement for them from BD.
I suspect that if your most technically challenging walking is going to be the CF, you might accept the compromises, and pay the extra cost.
BTW, if your current poles are not locking properly, cam based locks (eg BD's Flick Lock, Komperdell's Power Lock, etc) have a screw adjustment to tighten the lock when it becomes loose for some reason. If your poles have an internal expanding lock mechanism that you screw tight, you might try cleaning out any dust that has built up in the pole sections. It might be acting as a lubricant and either not locking or letting the sections slide together when under pressure. Follow the makers instructions if you can still find them. If not, use only plain water to rinse out the pole sections and let them air dry.