I owned a Z 155 Pro for a couple of years and sold it to a friend who also loves it. I am copy/pasting the the verbiage from the review I submitted to Pnet below. Ignore the fact that I gave the boat such a low numerical rating as it was strictly a response to the 1-10 rating that they use. Notice how all boats are rated 9 or 10 unless the seat is uncomfortable or the hatches leaks in which case they are 2's).
Bottom line for me is that the Z is a really great day boat.
Submitted by: chodups - Rating: 5 of 10
First off....this rating of 1 - 10 is so subjective as to be unmeaningful so I am going to rate my much loved and appreciated Z as a "5" to get your attention. It's a boat that performs exactly as you want it to when you are expecting a lot. So that makes it "5" right? "Meets Expectations"? Please take the ratings and throw them out. They are crap.
I've paddled both sizes of the plastic and glass Z's. I bought a 15.5 Pro when it became available. I'm 190 pounds and wanted a day/play boat. It has always delivered. The 16.0 and 15.5 are really similar but the 15.5 is quicker and plenty big. The 16.0 felt a touch too big and just not “special enough” to me. I read someone say that the 16.0 lacked the magic of the 15.5 and I agree, at least for my weight.
It has been a really good boat, particularly for rough water. The primary is very solid and the secondary is rock hard. If you stop to take a photo, grab something from the day hatch or use your relief bottle the primary takes care of you. No drama. If you get caught in something bigger than you bargained for it helps you out. Seems to me that the rougher the better. I have enjoyed it in surf and moving water and find that it accelerates quickly to catch waves. It isn't a fast boat but if you are racing in raggedy water it gives you an advantage over some faster (tender) boat/paddler combinations. Paddling with a couple of experienced paddlers in Coasters it seems easier for me to accelerate and catch waves that they don't quite get onto and it gives me an edge.
I have "raced" it three times and chose it for it's comfort, not it's speed. My goals in racing have always been to: #1 – Finish the race, #2 - Accomplishing that, not finish last.
I have always accomplished both goals but not by a lot. If you are after a fast boat, the Z isn't it. You can go 3 knots all day long, 3.5 all day long if you are fit and paddle well. Lots of boats do that. Yeah, you can spike a GPS at higher speeds but the bottom line is don't get a Z to have a fast boat. The beauty of the Z 15.5 is it's maneuverability and the comfort in water that requires consideration or help.
Example: This Summer I was in a downwind race with 2 to 4 foot windwaves. A much younger, more fit paddler in a Tiderace Explore beat me by 2 minutes after two hours. Many paddlers who had beat me handily in prior races on smooth waters fell behind. Figure out how that works into your priorities. Rough water is good for the Zephyr. It is pretty darn neutral in wind and the skeg does exactly what you want it to. You can tune little increments in and feel it unlike my Tempest 170 that isn't neutral and it's skeg is all or nothing and even at "all" it often isn't enough.
My complaints would include the front deck height and shape which sometimes interferes with my stroke a bit. Not a big deal. A personal issue, really. Yeah, another stroke class might help. Also, the very comfy primary makes you use more effort to edge it. You can get it way over and hold it with increasing resistance. A lower deck would help with the standard premium WS outfitting but a slightly less pronounced primary profile would be great for the advancing paddler and not so good for the new paddler who was buying his/her first boat and really wanted to make it count. This is the only boat I have owned, including my Tempest, where I have used the stock seat and outfitting. Friends who have paddled Explorers, Romanys, Quests, etc. love the responsiveness and control. I found that skills that had been challenging to master in other boats came easily.
As it is, I feel that the Z is a great first boat for that new paddler who is in it for the long term, plans on developing skills but doesn't want to be uncomfortable out of the gate. It doesn't have a ton of storage space in it so if you are planning a long trip where regular resupply isn't an option or your paddling partners want you to carry the two burner Coleman, extra fuel, a case of beer, firewood and personal camping gear you should look elsewhere. It's a day boat. The Z can accept intelligent choices that you would assume if backpacking "light". Sure, you can cheat, but don't ever consider it a trip boat. Think of it as a day boat that will take care of you and offer a solid platform for skills development while accepting your flaws.
BTW... Hatches are absolutely bone dry and required venting holes drilled in the bulkheads.