Yes. It is possible to use miCoach Zone with the Pacer with only one HRM and the Stride Sensor.
To do it, you will need to pair the HRM with both, the Zone and the Pacer. Please have a look at the next link. There you can see the instructions to do so: http://bit.ly/HQozK1 and http://bit.ly/J9BF2q.
Just make sure no other ANT+ compatible HRMs are close so they don't interfere when pairing.
Once they are set up, you will be able to see/listen your zones on both. Just make sure your zones match on the devices. It would be good if you first do an assessment workout with the Pacer and once your zones are calculated you can just input the value of your max. heart rate that you got on the assessment workout on the Zone watch.
As for the Stride Sensor, this only works with the Pacer.
The number of cubes within your status image is determined by your activity on the miCoach support website. These activities include (in order of importance):
Having a response to a discussion post marked as the correct solution.
Responses which are marked as helpful by other users.
