Not the person you asked but I have good data - I lost 32kg over 6 months on tirzepatide, 11kg of it was lean body mass, the rest was fat (based on DEXA scans).

In general, lean body mass loss is more of a result of rapid weight loss (I certainly consider mine very rapid), than result of the medication itself. If I was able to lose the same weight in the same period of time without the medication, and kept my protein and resistance training the same, I'd expect a similar ratio of muscle/fat loss.

Overall extremely happy with the outcome, very grateful that these drugs exist and that I was able to access them.