the indirect object

Den Touristen zeigt er die Kirche.

Can I say:

Er zeigt Dden Touristen die Kirche.

If either sentences are is true [/correct], which one is more commonly used by native German speakers?

Both are used. The normal and neutral word order is "Er zeigt den Touristen die Kirche." If you change the order, the part in front is emphasized. So the connotation is, for example, that he shows the church only to the tourists, and not to other people, etc.

"Die Kirche zeigt er den Touristen" = He shows them the church, but not other buildings, etc.

The exact connotation depends on the context.