i'm guessing the signal is impressed on to the power line in a "balanced" phantom cailho style. i don't know how to simulate that or how to extract it properly either in any simple way with proteus .
it doesn't look like Protues is simulating the true behaviour of the ZCD-pin
entirely possible, i never fully trust that it is fully realistic. it does however look like the zcd would work with an unbalanced ac signal provided the offset and magnitude are adjusted suitably.
zcd is NOT particularly useful for your project since it cannot drive a timer gate directly or be a capture source