just connect them together with a splitter in reverse.
Forgot the zenith silver sensor is not a traditional 300 ohm uhf yagi antenna it has a 75 ohm tap between the top and bottom element. the proper way to connect (2) zenith silver sensors would be to use a 75 ohm antenna combiner (not the same as a "splitter").
To reduce multipath when using coaxial cable splitters to combine multiple antennas start with the same coaxial cable length connected to each antenna. the longer the cables are the more this helps what you want is each channel signal from the antennas to hit the splitter at about the same time.
nighthawk, a zenith silver sensor has no reflector and not very directional if the antennas had a very good reflector or were parabolic dishes i would agree.