Can I connect two full thermostats to the same AC unit?

[ghurty]

My house was built in the 1990's.

The way it is set up in regards to the upstairs and downstairs, there is one unit outside, with two separate thermostats. (The basement has its own completely separate thermostat and unit)

The upstairs one will only work when the downstairs one is set to either cool or heat. If it is set to off, then the upstairs one wont work at all.

The upstairs thermostat has a W, Y, and two R's bridged together Picture Here

The upstairs thermostat is about 10 feet away from the circuit control board Picture here]).

Is there a way for me to replace the thermostat and connect it differently, so that the upstairs will work independent of the downstairs (that even if downstairs is on off, the upstairs one will work)? I would want to put the Trane TZEMT400BB3
upstairs (I believe it requires a "C" wire)

Thank You

 

[Desert_AIP]

ETA:
I can't see your first pic but it sounds like you have AC hot, heat and cold lines (R,W,Y) and no AC common (usually C - Black) or fan wirg (G - green)
(I figured it out, you left of the ".jpg" on your link - http://imageshack.us/photo/my-images/89/20110818153304.jpg/)

Is there a green on the downstairs thermostat? I don't see one wired in the second pic on Zone 1 (which I assume is downstairs).

Also, the second picture looks like a zone controller, can you take a better picture of the connections?
Can you read the brand and model?

I think you need to look at how your dip switches on the zone controller are set.
I bet they are in a master/slave relationship instead of dual masters.