code: public static <T1, T2, O> Flux<O> zip(Publisher<? extends T1> source1,
  			Publisher<? extends T2> source2,
  			final BiFunction<? super T1, ? super T2, ? extends O> combinator) {
  
  		return onAssembly(new FluxZip<T1, O>(source1,
  				source2,
  				combinator,
  				Queues.xs(),
  				Queues.XS_BUFFER_SIZE));
  	}
docs: Zip two sources together, that is to say wait for all the sources to emit one
  element and combine these elements once into an output value (constructed by the provided
  combinator). The operator will continue doing so until any of the sources completes.
  Errors will immediately be forwarded.
  This "Step-Merge" processing is especially useful in Scatter-Gather scenarios.
  <p>
  <img class="marble" src="doc-files/marbles/zipTwoSourcesWithZipperForFlux.svg" alt="">
  
  @param source1 The first {@link Publisher} source to zip.
  @param source2 The second {@link Publisher} source to zip.
  @param combinator The aggregate function that will receive a unique value from each upstream and return the
  value to signal downstream
  @param <T1> type of the value from source1
  @param <T2> type of the value from source2
  @param <O> The produced output after transformation by the combinator
  
  @return a zipped {@link Flux}