I have the Zena. Bought it some time ago, finally installed it, but still have to wire it up. I keep getting distracted. Currently distracted by a rear control arm that broke; trying to get it back on the road again...
Getting hard to remember why I chose it in the first place, but a couple things I remember...
It is its own generator, seperate from the vehicle alternator, I installed it so I can easily pop the drive belt on and off, so I don't wear it out not using it.
Completely isolated from the vehicle and it's electricals, I can weld on the truck without worries.
All self contained, no box to mount, which is important to me because I keep the fenders clear for easy removal for engine servicing.
All the controls are on the stinger.
A "boost" button on the stinger, allowing for higher current to strike the arc, then releasing the button returns to the set welding current.
Automatic truck throttle control.
And if their claims are correct, it should weld too

. Hopefully,some day I will find out.
gary