According to the question,
LX = XY = YN
XZ II LM
We have,
ar(LZX) + (XZY) = ar(LZY) — (1)
ar(MXZ) + ar(XZY) = ar(MZYX) — (2)
Both triangles LZX and MXZ are on the same base XZ and between same parallels LM and XZ
ar(LZX) = ar(MXZ)
Adding equation (1) and (2),
We get,
ar(LZY) = ar(MZYX)
Hence proved