The year is Universal Century 0087, and mankind has yet to be liberated from Earth's gravity. Seven years since the end of the One Year War, tensions between the Earth Federation and the space colonies continue on the rise. The police actions of the Titans, the Federation's military arm in space, fuel anti-Earth sentiment throughout the colonies and give rise to the Anti-Earth Union Group. Kamille Bidan, a young spacenoid from Space Colony Noa, soon finds himself in the middle of this armed conflict and behind the cockpit of the Titans newest weapon: the Gundam Mk-II.
After nearly 100 years of war between the nations Gilgamesh and Balarant, battle-weary soldier Chirico Cuvie finds his world utterly shattered when what seems to be a straightforward mission to infiltrate an enemy base turns out to be an attack on friendly forces. Furthermore, in the confusion that ensues, he stumbles upon a strange container with a beautiful woman sleeping inside. Unfortunately for him, he hasn’t just discovered any woman, but the key to a dark and complex political plot, and the perpetrators are determined not to let him live with their secret. Haunted by the memories of this mysterious woman and the betrayal of his superiors, Chirico must now fight to discover the twisted truths lurking behind the veil of war and gain new meaning to his bitter life.
If you loved how Zeta felt politically gritty and complex but also a little grim and serious, then definitely try Armored Trooper Votoms. It is aimed at a slightly older audience, with more realistic looking mecha and a stoic military hero who has to learn to open up. There are plenty of dogfights but it's all to a marvellously grim backdrop of harsh realities. The animation is not as good as with Zeta's but the more sympathetic characters and intriguing setting easily make up for it.
Classic 80's Sunrise mecha shows. While the storyline and characters aren't really comparable between the two, the shows do give off a similar kind of vibe and atmosphere. Zeta Gundam is often noted as being one of the darkest Gundam series out there with a very serious tone and so forth, and Votoms itself is very gritty, realistic, and all around consistently mature. Votoms has a trio of goofy and likeable characters for some comedic elements but at the same time, the show sometimes feels even darker than Zeta. Both tend to get a little supernatural by the end and it works really well. Chances are if you like one of these shows, you'll be able to appreciate and enjoy the other a lot too.
Sho Zama, an up and coming motorcycle racer, has been whisked away to the world between shore and sea, Byston Well. The world of Byston Well closely resembles medieval Europe with one exception: it contains giant robots called aura battlers. Brought to this world by the power hungry Drake Luft because he possesses the rare gift of aura, Sho is forced to fight in a war between two warring nations as an aura battler pilot. Can Sho find a way home, and what of the continually-expanding conflict?
Of all Tomino's non-Gundam works, Aura Battler Dunbine is probably the closest thing to basically being another Gundam, a medieval Gundam perhaps. Above all a lot of the characters and the general tone of the show feels closer to Zeta rather than the original Gundam series and others, so if you enjoyed the grimdark storytelling through Zeta and are a fan of Tomino's style, then definitely check out Dunbine. Oh and yeah, both are "Kill Em' All" Tomino for the record.
In the year 2075, humanity has spread to the stars, along with their technology, colonies, and... waste? At such great speeds in orbit, even a tiny bolt can cause a tragic disaster. Enter the team of the half division. Their job? To gather the garbage and debris that circles the Earth, in order to keep space safe. From broken-down satellites to bolts and nails, there's nothing that the underpaid and underappreciated staff can't salvage. Join Hachimaki, Tanabe, Fee, and the rest of the gang as they risk their lives to keep space clean, and keep their wallets... empty.
On the surface this might seem like a bizarre recommendation; Planetes is a show geared towards hard science and workplace relationships while Zeta Gundam is a mecha action series. However the political conundrums between Earth and space and terrorist organisations that evolve in both shows are strikingly similar, Planetes even uses a crisis that seems almost intentionally inspired by an event in Zeta Gundam. Admittedly Planetes is by far the superior show but Zeta Gundam isn't half-bad at all and well worth watching. If you're a Gundam fan and think Planetes sounds boring, it really isn't - you're sure to find it a lot of fun too!