Do Zuhl is a high-ranking scientist in the Boazanian Empire's Earth invasion forces under Prince Heinel's command. He possesses blue skin, a single horn, a hunchback, and a toothless appearance in the original anime, with later adaptations depicting dark brown skin. As Heinel's advisor and engineer, he designs and deploys mechanical Beast Fighters against Earth's defenders. His true allegiance lies with Emperor Zu Zambojil, who tasked him with monitoring Heinel and orchestrating the prince's assassination if he threatens Zambojil's rule, making Zuhl a concealed mole.

Cunning, manipulative, and intensely ambitious, Zuhl despises Heinel and schemes with Duke Zaki—another imperial agent—to undermine or kill the prince. He frequently boasts of his Beast Fighters' superiority and strategic brilliance, but repeated defeats by the Voltes team provoke Heinel's wrath, resulting in torture. While maintaining a facade of loyalty, he bickers with fellow aide Draco over influence and shares an initially trusting bond with Zandra until she uncovers his conspiracy.

Zuhl's assassination plots drive his narrative. In one scheme, he leaks weak points of Heinel's Beast Fighter to get the prince killed in battle, but Heinel's aide Ri Katherine overhears and foils the plan; Zaki dies in the ensuing fight. Later, after security footage exposes Zuhl killing an imperial investigator, Katherine devises a truth-serum interrogation. Zuhl spies through a hidden passage, panics, and attempts a direct assassination in Heinel's bedroom. Heinel anticipates this, using a decoy. Cornered by Heinel, Katherine, Jangal, and soldiers, Zuhl begs for mercy. Heinel spares him conditionally: Zuhl must eliminate the Voltes team to redeem himself.

This redemption proves a trap. Sent to the Voltes base as a false defector, Zuhl unknowingly carries concealed bombs planted by Heinel. The Voltes team disarms bombs hidden in his leg weight and staff. Enraged by Heinel's betrayal, Zuhl swears revenge and lures the team to a Boazanian underground base, promising an advantage. This leads them into Heinel's ambush. Zuhl falsely claims to Heinel he orchestrated this to prove loyalty, but Heinel denounces him as a traitor planning to use Voltes V against the empire. Zuhl attempts a final desperate knife attack, but Heinel deflects it. Heinel's guards execute Zuhl.

Heinel then orders Zuhl's legacy erased: every portrait, belonging, and record is destroyed, purging his existence from Boazanian history. Betrayal, failed schemes, manipulation, and ultimate erasure define his arc.