It is straight forward, although worded to confuse.
1) A motorised vehicle cannot overtake another motorised vehicle in the controlled(zig-zag) area, whereas a motorised vehicle can overtake anything else(including bicycles) in the controlled area.
A bicycle can overtake/filter passed any vehicle in the controlled area with the exception of the following law labelled 2.
2) No vehicle can overtake the vehicle closest to the crossing when that vehicle has stopped to allow someone to use the crossing.
That's not correct. The "driver of the vehicle" refers to "a motor vehicle". If it meant any vehicle including bicycles it would say "driver of a vehicle" not "driver of the vehicle". Therefore the subsequent two clauses refer only to motor vehicle drivers, not cyclists.