3-part separation.

The backpack's locking mechanism is pretty sophisticated.
First, the backpack is secured by two support struts that move in tandem, so it doesn't wobble loose easily.
The yellow arrow area completely locks the upper and lower body together so they don't come apart.
When attaching the backpack to the body, it's not just a matter of sliding the locking gimmick upward —
you also hook the backpack's ring onto the upper locking hook of the pin fixed to the body,
making sure the backpack never flops backward and falls off.
It's a bit hard to see in the photos, but anyway, it's a great gimmick. ^^;

In the old kit, the waist area was supported only by the Core Fighter,
which made it look a bit thin and flimsy.
In the MG ZZ, there's a volume-up part on the upper body that covers the top half of the Core Fighter,
giving the torso a much beefier look.

Unlike the Zeta, you fold the head antenna downward for transformation.

The beam rifle's grip folds neatly inward like this~

There's a little hatch that opens and closes on the head-mounting section of the beam rifle...

These are the pins that lock the rifle into the hole at the neck when stowing the head.
The old kit had nothing like this and was really loose,
but on the MG ZZ, thanks to this gimmick, the body and beam rifle lock together super solidly. That's MG for you!!

The arm transformation gimmick is pretty similar to the old kit, but the forearms are noticeably thicker,
and there's now a cover to hide the inner arm.

Even after the 180-degree rotation, the arm transformation gimmick locks in with pins on both sides, holding everything very firmly in place.

The shoulder slides out slightly to the side. It's extremely stiff, so be careful — you could snap the arm if you're not gentle.;;

To attach the Core Top's landing gear, you need to remove three covers temporarily.
Normally they completely cover the polycap slots for the landing gear 100%. Nice~

The completed Core Top.

Normally the Core Fighter also plugs into the back of the Core Top,
but I just left it attached to the Core Base side and shot it without it here. (You can't have it in both places at once anyway~!)

Locks in nicely — nice. It's got a bit of a fighter jet vibe.

Underside

The Neo Core Fighter. The transformation is perfect.
ZZ's Core Fighter is officially called the Neo Core Fighter.

Check out the color separation on the verniers.

Even that tiny little thing can have all its landing gear attached.

Those cute little wings are also retractable and poseable...!
Some of you might remember that on the old kit the wings were fixed,
so in MS mode you'd see them peeking out adorably from the sides. :-)

You probably remember how hollow and empty the inside of the old kit's big backpack looked.
On the MG ZZ, the inside of the backpack is properly filled out with volume and great detail too.

The leg transformation gimmick. The approach is pretty much the same as the old kit, but the rotating section is secured with a screw so it's much sturdier,
and the locking gimmick clicks together cleanly, making the transformation really crisp.

Yet another MG-exclusive locking gimmick!
The pegs on the underside of the backpack's verniers plug into the polycaps on the top of the transformed legs,
joining the backpack and legs together perfectly. A world apart from the loose old kit!

The wings on the sides are also articulated.

To attach the landing gear, you need to remove the cover on the nose section...

The landing gear cover on the knee section is implemented not as a removable piece, but as an actual opening/closing hatch — impressive.

The whole thing locks together solidly.

Underside

The fully transformed G-Fortress. It's massive at around 35cm.
View large image

Supported by four landing gear, it sits level without any trouble.

The backpack's missile pod opening and closing

The underside of the G-Fortress.