Now I got it!
The 555 is really an ingenious solution to the zero cross.
A few questions on the practical nature of this circuit
Is it more stable then LM311 for slow input signals (e.g 60Hz)? In other words, does it oscillate on the zero cross?
The reason why I am asking this, is that 555 might be a viable solution to using LM311 for my design (it looks like it is less bulkier than LM311 with a hysterysis feedback).
Just to recap, I've used the notes from application hints on LM311 to create a weak positive feedback (thanks TheOne), and I have had some very good results. The tiny pulses have decreased in amplitude, and the larger pulses are almost on the zero cross (within a few degrees).
Thanks for all the help!