The Laws of Cultivation: Qi = MC^2 - Chapter 53Book 2: : A Quiet Moment

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

Skyfire Avenue is a street that is 2048 meters long. There are 168 stores here, and each of the store owners is an extremely powerful adept. The Avenue does not permit any vehicles or any robots to pass through it, much less mecha. Even the patrolling police must move about on foot. This is because this is a street for pedestrians, a lane for nobles, hidden away within this high technology world. Lan Jue, the greatest of the mercenaries, code-named ‘Zeus’, has secluded himself here in Skyfire Avenue after the death of his wife. The name of his shop is “Zeus’ Jewelry Store”, and here in Skyfire Avenue, he has been given the title, Jewel Master.

Between heaven and earth lies the greatest truth, and the manifestation of the great truth descends in the form of Gu.　　People cultivate the Qi of heaven and earth around their bodies to control Gu and exert their magical power.　　One year after his transmigration, Chen Qing finally discovered his special features on the day he contracted his first Gu. He was actually able to see through everything about the Gu...　　Therefore, he began to march toward the road to immortality step by step.

After his fall, the Duke who was distant with his wife and daughter recalled his memories of another world. With a new perspective on life, he swore to cherish and protect those two.