Regressed with Omnipotent AI on Zombie Apocalypse(FF)

Ego responded promptly. "Sir, the simulations indicate that this fighter's maximum speed could reach Mach 6 to 7."

"That's more than enough," Zack said, satisfied. "Any faster, and we'd run into material limitations."

To achieve Mach 6, Zack had already incorporated a Ultralium alloy into the fighter's shell. Further improvements would require replacing the entire frame with the alloy—an expense even he wasn't willing to shoulder. "Alright, the design's good to go. Start production, Avalon F-2" Zack ordered.

With that, he deleted all related files, drawings, and holographic archives. There was no need to keep them once the manufacturing process began. Time passed quietly. Three days later, NYC was unrecognizable, transformed into a fortress of progress and security.

Outside the city, a network of sentry towers had been constructed. Each tower operated on an independent power supply and was equipped with highly sensitive optical sensors. The moment a zombie was detected approaching the city, the towers' automated machine gun turrets—fitted with silencers—sprang into action, neutralizing the threat. Stray zombies and even small hordes couldn't make it within a hundred meters of the city. For several days now, no zombies had been spotted near NYC.

If the struggling survivors outside could see this scene, they would likely be torn between envy and disbelief. Compared to the desolate outskirts, the changes inside the city were even more dramatic. Inside NYC, countless dilapidated buildings had been demolished. Construction vehicles rumbled along the cleared roads, hauling away debris. Materials that could be salvaged were recycled, and the rest was transported out.

The city's water and electricity had been restored. Streetlights illuminated the night, powered by a small Cold Fusion Reactor that provided energy to the entire city. NYC felt alive again. Each day, a fleet of trucks and dump trucks transported enormous quantities of resources to two major construction sites.

The first was the industrial zone, where production was in full swing. The second was JFK International Airport, Zack's newly planned hub for his ambitious projects. This was where Aegis, space-based satellites, Titan-class machines, and other large-scale projects were being constructed. In the industrial zone, the bug manufacturing plant had been operational for two days. Dozens of manufacturing bugs were being produced daily, exponentially boosting productivity.

This rapid development, however, came at a cost. The city's resources were being consumed at an alarming rate, far faster than Zack had anticipated. But to him, it was worth every ounce of material. At sunrise on the fourth day, four Avalon transport aircraft lifted off from NYC City International Airport. Each carried a completed space-based satellite module, heading across to the Rocket Launch Center.

While NYC was evolving rapidly, Zack had been taking it easy in his Mansion. Since the last battle, Sophia had grown increasingly aware of the vast power gap between her and Zack. Determined to bridge that gap, she had enlisted help over the past two days. Unfortunately, all her attempts had ended in miserable failure.

As the Avalons soared toward the rocket base, Zack reclined on a sun lounger, basking in the sunlight and admiring the girls training nearby. Sophia, as always, was flawless. But what caught Zack's attention were the surprising capabilities of two of the newcomers, Lily and Grace. Lily, in particular, was exceptional. The youngest, Mia, however, was a different story. At 17 years old, her performance was reminiscent of Annie's at 13—uncoordinated and clumsy. Of course, Erza still held the title of champion, her skills unmatched.

"Sir, the space-based satellite module has been delivered to the Launch Center," Ego's voice chimed in, cutting through Zack's leisurely observations.

"Already?" Zack raised an eyebrow, then muttered with a wry smile, "I guess time really move faster at holliday." With that thought, Zack shook off his laziness and switched to work mode. "Playtime's over," he announced, waving a hand before vanishing from sight. 

To the girls, Zack's disappearance was instantaneous, a blur too fast to follow—except for Annie, whose enhanced vision caught the motion. When Zack reached the basement, he called out, "Ego, is the high-energy particle accelerator almost ready?"

"Expected to be operational this afternoon, sir," Ego replied.

"Perfect. Once the satellite is in orbit, we'll start synthesizing new elements and build the Singulium Reactor " As he spoke, Zack donned his Apex armor. The suit's thrusters roared to life, and in a flash, he shot out of the basement garage, leaving a deafening sonic boom in his wake. Hours later, at the Launch Center, the final preparations were complete.

The last operational launch vehicle had been secured on the pad, its payload replaced with the space-based satellite module. Fueling was done, and all systems had passed their checks. The rocket was ready. "Begin the countdown," Zack ordered, watching from the control center with far more composure than during his first launch.

"Ten… Nine…" As the countdown progressed, reconnaissance satellites orbiting the Earth captured the scene. Zack's first rocket launch had stunned the world when it resulted in a devastating space-based weapon strike. Now, he was launching another.

Speculation ran rampant. "What could he possibly need another space-based weapon for?"

"Fighting zombies? That's like using a sledgehammer to kill a fly!"

Across the globe, leaders of various factions debated their options. Should they intercept the rocket? Was it worth the risk of provoking Zack?

While most hesitated, one base acted without delay.

At the Tianri Base of the Vanguard Organization in Japan, missile silos opened. High-altitude interceptors were locked onto Zack's rocket, ready to launch.

"Hurry! The headquarters has issued a order—this rocket cannot be allowed to launch!"

"Blackhand was killed by this man!"

"We must avenge him!"

"Why didn't we just send someone to assassinate him?"

"I don't know, but the headquarters ordered us to stop him. Maybe there's something about him they need?"

"Three!"

"Two!"

"One!"

"Fire!"

As the countdown at the Tianri base reached zero, the silo doors opened, and at the same time, the launch countdown from the base also ended. Rumble...

With a loud roar, the rocket shot into the sky, its tail leaving behind a trail of flames as it slowly ascended. What's worth noting, though...At this moment, Zack wasn't in the observation room. He was clinging to the rocket itself, lifted by its powerful force!

There was no other way. The Apex's top speed was Mach 8. To break free from Earth's gravity, it needed to reach Mach 23—7.9 km per second. To do that, multi-stage rockets were necessary. 

"Sir, we've detected critical information! The Vanguard organization on Japan is attempting to intercept your rocket!" Ego, who had been monitoring Vanguard's communications, reported promptly.