The natural asym fly vs. the synthetic:
Natural is the vertical (231P; 132C) and equivalent. The synthetic simply replaces the "ITM" bull call vertical, in the case of a 132C, with a bull put vertical. Long call vert = short put vert = box arbitrage.
XYZ 100/110/115 132 in calls = Long 1 100C/110C vertical; short 2 110/115C vertical. You're replacing the long 100/110C vertical with a short 100/110P vertical. Their equivalence is dictated by the arb.
Always try to dissect a complex book starting with the (calendars, then) verticals.