Canonical Zchar_opprPred := OpprPred Zchar_zmod.
Canonical Zchar_addrPred := AddrPred Zchar_zmod.
Canonical Zchar_zmodPred := ZmodPred Zchar_zmod.

Lemma zchar_trans_on S1 S2 A :
{subset S1 <= 'Z[S2, A]} -> {subset 'Z[S1] <= 'Z[S2, A]}.