First... STOP SHOUTING!
Second.... It depends on if it truly is a FM transmitter or just a FM Modulator.
Both are FM Modulators.... that's what turns the audio you want to hear into a FM signal. But if there is no transmitter stage after that, then you need to wire it directly into the FM antenna on the radio before the radio can tune it in. Just about every "add on" cd changer in the last 10 years has used this technology and I would think that any installer understands how this is to be wired.
If there is a transmitter, that means there is a modulator and then a transmitter which broadcasts the signal over the air. Then once you set the frequency any FM radio in a 10-30 foot radius should be able to pick it up just by tuning into that frequency.
One would think the instructions that came with the monitor would be able to tell them how to install it.
The thing that's getting me is the troubleshooting technique or lack of that CC is doing with this.
1. RTFM, set the frequency or find out which one it uses
2. If it's a transmitter,
2a. turn it on and see if the Z1 can hear the sound
2b. tune to a local station to see if the Z1 can lock on to that.
2c. put another FM radio next to the vehicle and see if that can hear it.
3. if it's not a transmitter, check the connections for the modulator (antenna wire into back of Z1).
Some say the FM performance on the Z1 is less than other radios, but it should be able to pick up either with no trouble.
If none of these work, I would start thinking you have a bad part, but you need (or they need) to employ some simple trouble shooting to figure out which part is causing the problem.
Without knowing the exact make and model of monitor, we can't look up the manual for it.