I suggest using either 2 Arduino pins, one for each detector or using a diode in series with the output of each detector.
Only in the case of devices with “open collector” type output can you safely join them together and this RCWL-0156 does not appear to be one of them. See GitHub - jdesbonnet/RCWL-0516: Information about RCWL-0516 microwave proximity switch module (ICStation.com SKU 10630)
It is very unlikely that these sensors will interfere with each other. These operate at around 3GHz and would have to transmit on the same frequency +/- a few kHz to interfere. Due to manufacturing tolerances, this is unlikely to happen.