# Applied Pi calculus: Evaluation context that distinguishes replication with different restrictions

For an exercise, I need to find an evaluation context $$C[\_]$$ s.t. the transition systems of $$C[X]$$ and $$C[Y]$$ are different (=they are not bisimulation equivalent), where $$X$$ and $$Y$$ are the following processes:

$$X = ( \nu z) (!\overline{c}\langle z \rangle.0)$$ and $$Y= !((\nu z) \overline{c}\langle z \rangle.0)$$

Intuitively, the difference seems to be that in process $$X$$, all replications of the process output the same $$z$$ on channel $$c$$, while in process $$Y$$, all processes output a different $$z$$. Is this correct? And how could this be used to construct an evaluation context such that $$C[X] \neq C[Y]$$?