Can I use two wireless microphone transmitters with one receiver?
No, this will not work. A wireless receiver can only demodulate the signal from one active transmitter at a time. But you may use one transmitter or the other, as long as only one transmitter is powered up at any time.
Operating two wireless mic transmitters on the same frequency simultaneously is the same as having two FM radio stations transmitting on the same frequency. The audio would be garbled and distorted as the signals from both stations interfer with each other.