On 25 August 2020, having been recalled from his planned two-year stay with Viktoria Plzeň, Herc moved on loan to another Czech club, this time joining Karviná for the 2020–21 season.[3] In summer 2021, Herc had signed a two-year contract with Grasshopper Club Zürich, who had regained promotion to Swiss Super League.[4]
On 25 July 2023, he returned to Dunajská Streda, following the expiration of his contract in Switzerland.[5]