dear azhar,
i understand your predicament. but if you can somehow manage to save a little space for a 14-pin DIP IC, then the IC324 can solve your problem. it is a quad op-amp IC and you can build the zero detector as wel as the monostable within the same IC, with just a few resistors that go with it.
i remember having fit the entire circuit(including the isolator) within a few square inches of board. for extra current, use a transistor as a driver..it works.