Zeroth law of thermodynamics in terms of heat

[Tosh5457]

Is there any definition of the zeroth law of termodynamics using the heat concept?

And does the zeroth law imply that the only way 2 systems can transfer energy is if they're not in thermal equilibrium? If 1 system is transferring energy to another one, that means they're not in thermal equilibrium right?

 

[atyy]

Yes.