=  replacement or .. statements

When statements like

x(i)=4;

Eq4[I].. zZ(i)=e=12/x(i);

are included in a GAMS code all of the cases associated with each and every element in I are computed.  The order that the calculations or done in terms of the elements of the sets depends on the order of the set elements as discussed in the Rules for Item Capitalization and Ordering chapter.