So just the enviro diaphragm? So the reg still breathed fine then. The DS4 that I know of blowing up in a parking lot, actually rendered it unuseable, and I have also heard of others doing it. My opinion on Zeagle regs is based on over 100 dives with my Zeagles, in everything from the tropics, to ice dives, and they are the only reg I've used, or my buddies used, that haven't ever given them even minor issues.
If I had to wager I guess, I'd assume that the enviro cap blowing off had something to do with the service, and not the reg itself. If there was an inherent problem with them from the factory that would cause that to be a regular occurance, you can rest assured that Zeagle would rectify it. Just as Apeks has issued recalls to rectify any problems they have had.
Long story short, my trust (and MANY others here on the board) in Zeagle regulators is based on personal experience, using, servicing, and being treated well by the staff at Zeagle. We all have been "burned" by a product at some point, and once that has happened, you tend to write off that particular thing, but I found it a little arrogant to spout off blanket statements like "they are a bad design and tend to blow apart underwater" when you have one confirmed report, and some hearsay about an event that doesn't result in any catastrophic failure mode.
Case in point, Oceanic had a major recall from HP seats splitting. Now that would be a catastrophic event. They issued a recall, fixed the problem, and moved on. No scuba manufacturer is infallable, including Apeks, who have a recall out currently.
To the OP, do some reading on here. You'll find tons and tons of extremely satisfied Zeagle reg users, and extremely few unhappy ones, and in the event that there was some kind of issue, Zeagle has possibly the best customer service in the industry, which is a lot more than can be said for Apeks/Aqualung.
Jim