I have been using the ZEV Pro Magwell for over a year now. I highly recommend it. I do NOT recommend the ZEV Pro Plus.
I have found the ZEV Pro magwell works with most magazine extensions available on the market, but certain extensions will hit the magwell when slammed into the gun. As an example, the TTI extensions using a pin to retain the extension on the magazine will hit the plug area of the magwell when inserted, if the pin is positioned higher. Falkor Velocity extensions will also hit the edges of the magwell. I have had both TTI and Falkor magazines stick in the magwell from being slammed in there. This is a reason I do not advocate competition magwells without magazine extensions. If the magazine gets stuck, you need to be able to rip it out.
As you can see in the photos below, the ZEV Pro is extremely generous for its small size when compared to the much larger ZEV Pro Plus. In the photo on the right, you can see where the marks from the extensions have hit the ZEV Pro. In the third photo, you can see where the same extensions have impacted on the ZEV Pro Plus, but have resulted in much deeper gouges.
I have used many different extensions, but I prefer the Henning Group Blue Line +4 Extension over all others. It is not as high of a capacity as the others, but it is much slimmer, includes "feet" to ensure a solid purchase to rip the mags out if needed, and it DOES NOT hit any magwell that I have tried it in.
From left to right: Glock 17 round factory magazine, Glock 17 round magazine with a +2 factory extension, Henning Group +4 Blue Line Extension, Falkor Defense +5 Velocity Extension, Taran Tactical +6 Extension.
I do not recommend the Falkor extensions only due to size and weight. They function very well.