Issues.

One, you only posted the DDL for one synonym, but enough on that.

Two, it is looking like the "tables" may actually be views not actual tables.

Three, and I may be wrong here, but you are going to be pulling the data from all the tables referenced across your network to the server running the query where the respective joins and filtering will then be completed.

At this point we really can't do much until you provide the underlying DDL for objects referenced in the query.