CM is Countermeasures. Normally it would have either an 'A' or 'P#' More advanced races usually have both.
A is Active Countermeasures. Nearly all vehicle in DzC have active countermeasures, and as the name suggests, they are active all the time.
P is Passive Countermeasures and will usually have a number behind it. After a hit is scored against a unit with Passive Countermeasures, the controlling player rolls 1 d6 for every hit scored. The number after the 'P' is the score required to negate the hit. For example, most Shaltari vehicles have A,P5+. Giving them Active and Passive CM on a 5+
Passive Countermeasure rolls are made after hits scored, but before the damage rolls are made.
R(F) and R(C) are weapon ranges. The (F) is the maximum weapon range. (C) is how close you have to be before the enemy's Active counter measures are ineffective.
For example. You fire a shell or rocket at an enemy. Their active countermeasures will shoot down, block or otherwise prevent the ordinance reaching it. But if you are close enough to the enemy that their Active Countermeasures do not have time to react, then the shot hits the intended target.
Yeah,
AC is Accuracy. Exactly the same as Ballistic Skill in
40k. But there are modifiers that make the shot harder or easier.