The legs seemed like a good place to start on this kit. This is a bit of a general overview, a ton of work went into the legs.
I wanted the pointy feet that are a prominent feature on the 80's Model Graphix version. I extended the toes using sheet styrene top and bottom, then filled the gap in the sides with epoxy plumbers putty. I extended the heel with plastic and epoxy as well. The bottom is detailed with plastic sheet. I installed a Wave double ball joint for the ankle. The socket is embedded in the leg with epoxy putty.
The Sentinel book version also had very long knee pieces. I sawed off the original kit knee and fasioned new ones from styrene sheet. Per the original Katoki lineart, there should be a vernier box on the back of the legs. This too was built from plastic sheet. It was necessary to saw the standard ZZ rear leg vent off of the back to fit the new piece.
This older style kit didn't have any horizontal rotation at the hips. This is an easy fix since ZZ has a seperate hip section built into the design. I sawed off the top of the hip section, embedded a polycap in the thigh with Bondo, then capped the thigh with plastic sheet. The hip was reattached with a plastic peg that connects to the polycap.
Here the planning for the removable Full Armor parts began. The outer leg armor included with the kit is just a left/right assembly. I cut away the "shin" from the armor pieces and made a new one from plastic sheet. This new shin armor can be attached to the leg via a polycap I put into the leg, and is swapped with the "normal" ZZ piece when the armor is removed (there wasn't room or mechanism to attach it over the top of the standard piece). I had to do some tweaking to the lower edges of the armor here using sheet plastic to thicken them.
The vent/vernier which should be "covered" on the outer side of the circular section of the legs is removable via two small brass pins and sockets (the original kit has you just leave this off to accomodate the armor). I glopped Bondo polyester putty into the armor pieces and squished them into place on the inner legs to achieve a tight fit, the sanded the inside a bit to prevent paint scratching. A thin sheet of metal was embedded in the side of the leg then puttied over, and a rare earth (neodymium) magnet in the armor. The magnets hold the armor in place.
I used to pre-scribed plastic sheet to add detail to the large vents on the outer armor. A bit of scribing around panel details, a few chiseled greebles, and the legs were done! (a month later)