Just 13 minutes into the game, John van den Brom’s men took the lead through Japan international Junya Ito, who drilled a close-range shot past goalkeeper Sammy Bossut after he was set up by Colombian defender Daniel Munoz.
On the stroke of halftime, the visitors were rewarded for their dominance as Kristian Thorstvedt doubled their advantage.
Munoz recovered the ball before passing to Ito who teed up the Norway international who sent his shot past a helpless Bossut.
Two minutes into the second half, Onuachu extended Genk’s lead with Ito providing his second assist of the high scoring encounter. That was his tenth league goal of the 2021-22 season.
Five minutes later, captain Bryan Heynen made it 4-0 with a cool finish before Jhon Lucumi increased the lead with a beauty.
Not willing to go down without a fight, the hosts reduced the deficit through Jelle Vossen, who was assisted by former France youth international of Malian descent Jean-Luc Dompe.
On loan Reims midfielder Dereck Kutesa made it two goals for Francky Dury’s side with a cool finish which goalkeeper Maarten Vandevoordt had no chance of stopping.
Genk sealed the comprehensive victory through Heynen, who completed his brace with four minutes left on the clock.
After playing for 80 minutes, Onuachu was subbed off for his compatriot Ike Ugbo while Ghana’s Joseph Paintsil was introduced for Belgian star Luca Oyen at the same time.
On the other side, Idrissa Doumbia was introduced for Abdoulaye Sissako in the 46th minute with Senegal midfielder Ibrahima Seck seeing action from start to finish.
Whereas Cameroon’s Frank Boya and Gambia’s Alieu Fadera were not listed for action.
Thanks to this result, Genk moved to third on the log having garnered 20 points from 13 matches as Zulte Waregem crumbled to 14th with 13 points from the same number of outings.