The simplest thing would just be to DFA Zimmer today for Harper (Castellanos back to RF, Vierling plays CF for one night) and then swap Munoz for Marsh, though yeah, they do have the Eflin move.
And the move for Falter was Wheeler. Sanchez is either staying in the pen (which they were considering) or they can bring someone else up.
You only get 2 extra players on September 2. One arm. They also might be better off letting Hall continue to play every day until the AAA season ends.