I've come across this a few times and have yet to find a general consensus on how to format a proof inside of a proof. Should there be a proof environment within the proof environment that is indented? Should there be a different QED.
This thread somewhat talks about an approach, but cases are a bit different that "inner proofs".
I checked AMS' Mathematics in Type but it had no mention of such a scenario.
lemmaenvironments outside your main proof; no need for too much nesting. – jub0bs Mar 10 '14 at 07:38amsmathtotheorems--amsmathdeals mainly with the formatting of display math; it has nothing to do with theorems. and i used a more generic tag thanamsthmsince there are several available theorem packages. however, the topic is still better suited to the math se. (the ams doesn't have a specified format for this situation. i've seen proofs "discontinued", other material including proofs inserted, and finally the original proof completed; but there wasn't any indentation, just explanatory prose and a final tombstone.) – barbara beeton Mar 10 '14 at 14:04