Is it permissible to combine prayers and perform them after 9:00 PM upon leaving work, due to the difficulty of performing prayers on time during work from 9:00 AM to 9:00 PM in a store in America?

A Muslim must perform every prayer at its legally prescribed time. It is not permissible to combine all prayers, nor to combine two prayers together. For "Indeed, prayer has been decreed upon the believers a time-bound ordinance," meaning it is obligatory at its prescribed time and is not valid without it. Performing prayer does not require effort or time that would constrain work time, and Allah Almighty has made our religion easy and has not placed any hardship in it.