Complex sentence: Equation (1) makes a cyclic process similar to an isothermal process: even though the internal energy changes during the course of the cyclic process, when the cyclic process finishes the system's energy is the same as the energy it had when the process began.
Split into simpler sentences: Equation (1) makes a cyclic process similar to an isothermal process: even though the internal energy changes during the course of the cyclic process when the cyclic process finishes. The system's energy is the same as the energy it had when the process began.