Nearly everyone is exceeding ISO 4210, the lowest safety factor I've seen is 1.5x, but passing the standard doesn't guarantee reliability. A QA program requires statistical sampling and understanding the failure rate, etc. That is going to be a huge input into reliability and recalls, likely as much as the design. I also don't know how relevant that ISO test is with tubeless, but that's for someone smarter than me to figure out.
I've never worked with Zen, but nearly a year on, I am pleased with my wheels from DFS. I'm a fan of THR Industries hubs, and I don't regret getting them built with steel spokes. After completing a bunch of aero testing, the results have me selling a couple of my other wheelsets and sticking with these as both an all-around and an aero wheelset. I dove into their catalogue to find a front wheel profile that matched the original HED Toroidal patents' general profile, and paired with the Aero 111, it's a fast and stable enough setup for my uses.