Scenario 1) Base Bazz and Base Robert vs Shikai Renji and Shikai Rukia Scenario 2) Vollstanding Bazz and Sklaverei Robert vs Bankai Renji and Bankai Rukia
I would honestly give it to Robert and Bazz-B with High Difficulty.
The Anime actually states Rukia's Bankai takes a HELL of a toll on her and thus if she fucks it up, she's done for completely.
Meanwhile we know Renji can take on a Sternritter by himself but he still needed to rest after that(Well the Anime doesn't take that into account) but we have no idea how well he does against 2 of them and Bazz and Robert aren't weaklings either.