Just like fillerpachi, Zaraki's riatsu severs as a defensive armor that protect him from all sorts of hax.
Acording to shien(the enhanced version of Sayza appolo, the one with same amount of riatsu as h2 Ichigo), when Zaraki's fighting him, Zaraki's strength at the moment is so strong that he could easily blow away Baragan's respia and stark's wolves. (and since zaraki's riatsu=shien's riatsu=h2 ichigo's riatsu at this moment, i suppose h2 ichigo can also do this. maybe that's a confirmation that h2 ichigo is stronger than all other Espadas?)
Shien also used the voodoo doll on zaraki, he created dozens of them, but all of the dolls were too hard for him to break, so yeah even if you have same amount of riatsu as zaraki, your hax still won't work on him
During the fight between zaraki and 8th kenpachi, he endured hunreds of itto kaiso(The 1 Yama did on Aizen to kill him) without much of damage. Even 8th kenpachi's ability, whichi fuse himself against his opponents and break their bodies from inside, is nullified by zaraki's riatsu.
and finally, in the final bout between zaraki and the 8th kenpachi, none of the other spectators were able to sense their riatsu, which may suggests that both zaraki and 8th kenpachi are at transcendent level (at least in this final moment)
oh, and the amount of riatsu his eye pad now absorbs is 10 times more than before the time skip...