What is the Sharia ruling on an employee selling his company's cars to a colleague and splitting the profit, knowing that the company does not give a commission on sales, and what is the ruling on the colleague borrowing money from the merchant from whom he will buy the car?

You are not permitted to take a profit from selling the car except with the company's permission, as you are its agent. Your selling the car to your colleague is permissible unless it involves favoritism or the company prohibits it. Your colleague's selling the car to the merchant who loaned him its price is not permissible if it was a condition for the loan.