Bridging NAD 3155 and 2155 to include a subwoofer

How do I bridge an NAD 3155 and 2156 to push NHT Super Zeros and NHT Super 8 sub? The only thing I can figure is to run y adapters from the pre out to the sub. Help would be greatly appreciated. Thanks

No one is offended and your additional information is appreciated. Before responding to this post, I looked at the back of the sub and there was no indication it had a high pass filter. Then I did a search for "NHT Super 8 manual". First choice was Crutchfield, nothing listed in features, download the manual, nothing there about high pass filter, although it stated for more information, see online manual at I go there and download, even less pages than the Crutchfield download, still nothing. So, I had to assume no high pass filter. About the bridged hookup, I apologize to you and OP, brain f**t, and just put all of that foot in my mouth.

Now, and I think you will agree, the best way to connect the OP equipment is to use the 3155 only with it’s output to "High Level In" on the Super 8, then "High Level Out" from the Super 8 to each Super Zero. Crossover set at just below 120Hz, according to the manual. The 3155 should be more than enough power for the Super Zero’s connected this way and the advantage of having them high passed far outweighs the advantage of extra power and playing them full range. Actually the overall system capability should be greater in high passed configuration since there will be much less chance to overdrive the Zero and bottom out it’s small woofer.

Thanks all for the great information. After reading these posts I've decided that it's overkill to run the 0s and sub bridged. The 3155 already makes them zing. 
NAD recommended using pre-out but also said it was acceptable to run cable from 3155 to the high level end in and then run to
0s from low level out. 
I think they sound better running the wire and skipping the pre- out.  Thanks again for all the info.