First we prove the equality
C1DB1E=C1A1B1A1.
Since the quadrilateral XB1CE is cyclic, ∠XB1E=∠XCE. Therefore, the triangle BB1E is similar to the triangle BCX. Hence,
XCB1E=BCBB1.(1)
Similarly one can prove the equality
XBC1D=BCCC1.(2)
Hence, dividing equation (1) by equation (2), we get
C1DB1E=XBXC⋅CC1BB1.
Applying Menelaus' theorem to the triangle XB1C and the line AB we obtain
CC1XC1⋅AB1AC⋅XBBB1=1.(3)
Further, the same arguments applied to the triangle CC1B1 and the line AX imply the equality
B1A1C1A1⋅ACAB1⋅XC1XC=1.(4)
Thus, multiplying equalities (3) and (4), we obtain
C1A1B1A1=XBXC⋅CC1BB1=C1DB1E.

FDB1F=C1DB1E=C1A1B1A1,
so A1F∥C1D.
Suppose that the lines B1E and C1D intersect at point Y. To prove the statement of the problem it is sufficient to show that the lines YA1, B1D and C1E intersect at the same point. Let us prove the equality YD=YE. Indeed, since the quadrilaterals XB1CE and XC1BD are cyclic,
∠DEY=∠CEB1=∠CXB1=∠C1XB=∠C1DB=∠EDY.
Therefore, the triangle YDE is isosceles. Since
B1EYE⋅C1A1B1A1⋅YDC1D=C1A1B1A1⋅B1EC1D=1,
so Ceva's theorem implies that the lines YA1, B1D and C1E intersect at the same point.