This kit is the Endless Waltz version of the Gundam Wing Zero, which has been piloted by... pretty much all the characters in the shows at some point or another, but most notably by Heero Yuy.
Design wise, the difference is that it's sleeker than the TV show and the HG version.
The "proto" is only relevant in the sense that it's what the zero would've looked like before the Zero Custom with the angel wings, in Endless Waltz.
While this isn't a "ver ka", it's a Katoki kit through and through, with a slimmed down design and more aggressive angles.
It comes in the classic Gundam colors:
Slightly dark/desaturated red, a near navy blue, white, pale yellow and transparent green, as well as an inner frame grey.
While the plastic isn't full of details, there are plenty of opportunities for panel lining.
The kit comes with a sticker decal sheet and dry transfer sheet with the usual Katoki angled lines, stripes and warning letters in red and white. There is a small sheet of reflective stickers for the eyes and the cameras, however the latter are all transparent green and don't need them. A single silver sticker goes behind the chest gem, which brightens it up.
It's a 'Wing Gundam', so it has wings and a bird mode.
As usual it's a 'twist the torso and put the shield over the head' partsformation, as all the wing bird mode transformations are, but it does it a little better than most.
The legs split open and shift to turn them into rear thrusters. It's better than just angling the toes and pretending they're not legs.
The shield has a pair of wings that fold out and a flap that hides the head from below.
The twin buster rifles hang from the shield as a pair of mounted guns.
There's a couple of things that pull out and fold or unlock, to move things around to get a sleeker looking bird mode. The two wing pods fold out to reveal a large thruster underneath each.
The articulation is on par with the other EW Wing kits, but the legs feature more panel separation and all limbs have slightly better angles of movement.
There are little wings on the side skirts (I have no idea why, they're not for the bird mode, it's just a fun detail) and all skirts move around on two joints.
There are two pods, one on each shoulder of the torso, that open and reveal gatling cannons.
The cockpit pulls out to reveal a sitting Heero Yuy inside.
1 Shield, attachable to either arm with two wings geared together that open and close.
2 'Twin Buster' rifles that can combine into one.
2 Beam sabers that store inside the shoulders - The white top parts open to reveal them.
2 Green 'blade' style beam effect parts.
4 Pairs of detachable fingers, 2 open palms, 2 beam saber holding hands, 2 gun holding hands and 2 fists.
1 Heero Yuy 1/100 mini-fig standing in his tank top and shorts.
You also get a simple stand that plugs into the back of his wing back pack or you can attach a 'shell' that holds the model in its bird mode. The shell plugs into the back skirt of the model, but make sure it's attached properly, otherwise it's easily knocked off.
There's also a holder for the crotch for other bases/stands.
There's a handful of different 'Wing Gundam' designs.
You have the TV Wing Gundam, the TV Wing Zero, the EW Wing Gundam and the EW Wing Zero Custom - This is an EW design of the TV Wing Zero with the added 'proto', to inform you that it came before the Custom version.
It's confusing, I know. I've been a fan of 'Gundam Wing' since the mid 90's and I still occasionally get it wrong.
There's a few tiny parts in the shoulders (little grey vents) that pop out occasionally. The construction is good, but not great, the tolerances are a little looser than a 2013 kit should be.
This is a nice 'Wing Zero' kit with a good looking and maybe the best 'bird mode' (certainly the legs are the best).
If I could only have one model out of all of the different versions, I'd pick the newer 'Wing Zero Custom Ver. Ka.' which is more solid and has more and better mechanics (and also comes with a stand).
However, the designs and colors are different, there's a lot more red/yellow on this and I'd argue this version of the twin buster looks better too.
If you don't like the 'angel wings' then this is the definitive Wing Zero kit.
The best 'Wing Gundam' kit (not zero) is the gorgeous 2021 RG #35 Wing Gundam.