Itachi and Zabuza should win this battle. Zabuza can be easily defeated by Tsunade considering her incredible raw physical power and medical ninjutsu and though Zabuza was for a moment a good opponent for Pre-Shippuden Kakashi he should not be able to fight Tsunade for various reasons. Tsunade's physical strength should overwhelm Zabuza greatly as it has allowed her to lift Gamabunta's colossal sword countless feet in to the air and in turn used it to incapacitate Manda (The gigantic snake Orochimaru is able to summon). Tsunade's apprentice Sakura was shown to be sufficiently strong enough to hollow out an entire mountain with a single punch and it should be noted that Tsunade is far stronger than Sakura so one could imagine what monstrous strength she possesses. In addition to her unrivaled strength her physical durability is also impressive, after having her muscles torn she was still able to move properly something that gained praise from Kabuto. For a shinobi with monstrous physical power she has also displayed tremendous amounts of speed and she is one of the most powerful taijutsu masters in the Naruto world. Aside from her physical prowess she is a master in medical ninjutsu and with her Creation Rebirth technique she is able to heal countless wounds, grow back missing organs and regenerate cells in her body, this technique makes use of her Yin Seal: Release and though it does consume massive amounts of chakra it is an effective technique in battle. Tsunade's chances of winning against Zabuza are further increased due to her summoning abilities.
Deidara should prove to be short work for Itachi. During their first encounter when Deidara was located by Itachi, Kisame and Sasori so that they may recruit him into Akatsuki under the orders of Pain (Nagato), Deidara refused to join and stated that only if Itachi defeats him in battle he will accept and so this resulted in Deidara battling Itachi resulting in Itachi easily defeating Deidara by using his Sharingan. Itachi should not even exert himself against Deidara and should effortlessly defeat him considering his vast array of jutsu and his Mangekyou Sharingan.
This team battle would eventually boil down to Itachi Vs. Tsunade and the outcome would be Itachi leaving the battle as the victor. Itachi is an extremely powerful and dangerous ninja being able to easily defeat Deidara, Kakashi and Sasuke. Itachi was noted by many as being ridiculously fast in movement and in using his hand seals, his speed was so high that not even Kakashi and Sasuke who are quite skilled in using their Sharingan could follow his movements, Itachi has a great diversity of jutsu having mastered all of the Uchiha Clan's jutsu and more. Itachi's mastery with his Sharingan is his most dangerous ability, Itachi could trap Tsunade in a dangerous genjutsu and if he were to activate his Mangekyou Sharingan using Tsukuyomi against her should overwhelming for Tsunade as a single Tsukuyomi was sufficient to bring Kakashi close to death and after the technique was used on him Kakashi entered a comatose state. If Itachi were to use Susanoo or Amaterasu he should be able to quickly defeat Tsunade. A Pre-Mangekyou Sharingan and fresh Sasuke (during his final battle against Itachi) with prep struggled greatly against a dying and drugged Itachi who had been holding back greatly during the fight as noted by Madara Uchiha who stated that if Itachi were serious he would have easily killed Sasuke. Team One wins.
Itachi might solo but would definitely win with Zabuza. Tsunade is the difficult element of this battle. The three sannin were close to equal however Orochimaru with injured hands was able to hold his own against the other two sannin simultaneously however Itachi was able to easiliy beat Orochimaru twice whereas he was apparently terrified or Jiraya even with Kisame there and fled. Now back to the point, of the three sannin; Tsunade appeared the weakest to me so I think that with effort Itachi could beat her meanwhile Zabuza is able to at least hold Deidara off until Itachi gets there and easily dominates him.