MTL - Warhammer: The Beginning is the Crisis of Annihilation - Chapter 343 Middenheim's Freshmen (subscription required)

A con-man and policewoman that are legends of their respective professions suddenly die, then are reincarnated and return to the Tang Dynasty of ancient China as little kids.

Accepting their second chance and forced restart, they choose to use the modern knowledge and specific talents that they have in their previous lives in order to live comfortably in this new life.

- Description from Novelupdates

The apocalypse descends, zombies and monsters appear, followed by System Leveling, which grants skills to all survivors.With the collapse of law and order, some become powerful while others remain weak, and so the dark ages begin.

Lin Tianlong, 19 years old, a polytechnic school graduate. With mastery and control over electrical energy, he displays his unparalleled sagely medical skills, accepting the hearts of beauties on the side. Starting by helping his sister-in-law’s small clinic which was on the brink of closing down rise from the dead, he then proceeds to bring prosperity to a private hospital previously in a business slump. Socializing among the officials from the sectors of politics, commerce, law, literature, education, and health in Flame City, he’s drawn into the power struggle between the officials. Businesswomen, doctors, and nurses, attractive policewomen, teachers, pretty loli girls, charming married women, mature beauties – all of them fall to his clutches as he establishes his business empire and a harem of beautiful women.

- Description from Novelupdates

Ash Crowner was your ordinary college student with little to nothing going on for him.He lives a carefree life with no worry for what is to come. But theres one thing he lives by: PAYBACK.He always gives back what he’s given, either twice as hard, or hotter than hell.However, his life takes a dark turn when he is lured to a secluded spot by his peers, leading to his tragic death.But they say where one thing ends, another begins.The curtains didn’t close there for Ash. He was judged and transmigrated into the most hated man in another world.A young king reviled by all. A man disgraced, hated by his wives, and ignored by his court.With an enigmatic system by his side, Ash now has to live a whole new life as someone else, all while kept on a leash by the higher powers—the judges, that dragged him into this new world.He has to earn his due respect, rebuild his image, and also unlock the mysteries surrounding him, including the unexplained death of the young king he transmigrated into.But among the many things he’s set on doing, two stand above the rest: repaying the suffering inflicted on him by the judges who brought him here, and avenging the untimely death caused by his peers in his previous life.Follow Ash as he claws his way from disgrace to glory, in a world where second chances come at a deadly price.