That’s what I found odd about the Apollo 13 mission. On the way back, they famously used the LM descent engine to speed up and position the whole Apollo assembly. That meant you had the massive service module and command module on one end (yes, zero gravity, but with lots of mass) and an engine at the bottom of the LM at the other. In between was a light tin can, the LM ascent stage. How did they do that without the LM in between being crushed, or at least distorted?
On the way to the moon you had the service module engine pushing the whole LM assembly, so you can assume there was reasonable structural strength. Plus I’m sure they throttled the LM engine carefully.