You won’t get the planetary performance Z12 is able to provide out of the box. This is due to the low-quality, 9mm Plössl eyepiece. It is nowhere near enough for a telescope this size.
With a decent planetary eyepiece such as a Goldline, you get an insane planetary performance with Z12. I will assume a decent planetary eyepiece in this section, but with the 9mm eyepiece, expect half of the performance I will write below.
Jupiter’s many stripes, The Great Red Spot, and its 4 Galilean Moon’s will be crystal clear. The moons will appear as spheres instead of bright disks. The color accuracy you will get will be on-point, with gorgeous shades of beige, yellow, red, and brown.
Rings of Saturn will show its separate lines, with Cassini Division easily observable in the middle. There will be some stripes around the planet, and the yellowish color of the planet will appear. Its many moons will appear, and its largest moon Titan will show itself as a disk.
Mars will show a significant amount of surface detail as red, black, and white stains. The white stains are the ice caps, and the black-red colors are due to the nature of the surface. You can get a glimpse of its moons as well.