Exercise: As it exists, this system works relatively well, but it could be further refined. See if you can spot some design details that would provide equal or better performance while using less hardware.
Moving to the right side of the buffer tank we find a “primary loop” with its own circulator. However, the zone circulators are not connected as secondary circuits (e.g., they are not connected using closely spaced tees). This arrangement can cause heat migration in the parallel-connected zone circuits due to head loss around the piping loop whenever the primary loop is operating.