Here is some troubleshooting information to solve the issue.
If your air handler is displaying P5 error code which are specially for multi-zone, this initiates a conflict mode meaning that one of your indoor units is calling for cooling and the other one is calling for heating mode.
Unfortunately they are not able to operate on different modes, at the same time. To have this problem resolved, you can reset your unit by unplugging the breaker for 4 consecutive hours, so that the capacitors completely discharge.
You can also set all of your indoor unit on cooling mode and have them run together for a short period of time.