@gently I mainly rely on Dr/ Ben Leder's video on Combination and Sequential Approaches to Osteoporosis as well as McCormick's "Great Bones."

Leder says combining Forteo and Prolia has dramatic effects. Forteo first (for 9 months as I remember) with Prolia coming on and intersecting. His video says that combining Forteo with a bisphosphonate does not improve over either alone.

All the sources I have seen say that Forteo and Tymlos are ineffective after Prolia and should not be considered.

Leder's videos have a lot of graphs and charts that make all this visually clear. I am relying on memory so check them out. He is a leading MD and researcher at Mass. General in Boston. He is also on OsteoBoston on You Tube.

These positions conflict with those in the study posted by @gently. Here is the conclusion in that:
"It is clearly time to re-evaluate the potential benefits of combination therapy, with a careful attention to effects on both spine and hip. In patients who have previously received bisphosphonate agents, there is no question that different results are achieved at the hip and perhaps other sites rich in cortical bone with combination vs individual therapy. The current study by Walker et al. adds to the growing literature that suggests that even in patients who have not been on bisphosphonate treatment previously, a superior hip BMD response might also be achieved with combination therapy (in this case, teriparatide plus risedronate). These differences might be clinically meaningful, particularly for patients at highest risk for hip fractures, including those who have had a recent hip fracture, multiple prevalent fractures, or extremely low hip BMD."

This clearly challenges the oft cited idea that bisphosphonates reduce effectiveness of anabolics.