The power supplied at the input will be equally devided to the input of the amps. Nil power will be arrived at the 50 ohm
load. The power what goes to the lower amp is -90 degrees, the power what goes to the upper amp is -270 degrees shifted
is phase. The power at the 50 ohm load via the 3/4 and 1/4 75ohm line is -360 degrees shifted. The power via the other way (1/4 and 1/4  75 ohm line) is shifted -180 degrees. The result is they are 180 degrees out of phase and cancelled !
For the output ring counts the same.
The big advantage of this system the INPUTS of the output ring are isolated!
The load at the outputring must can handle 1/2 the power of either amplifier. When one amp fails half of the power of the other amp will go into the load. a tip!! incase of a 50 ohm dummie, you can a  connect a dipole or another 50 ohm antenne.

ALL transformers are made of 75 ohm coax cable ( don't forget the velocity factor!)