Jiraiya would be carrying the team like how Kakuzu carried his.
-Jiraiya deserves a better teammate ie. Kakashi, Gai, Tsunade etc.
i think you're underrating Zabuza, he has the hidden mist jutsu with accordance with Jiraya's sage mode can provide a very deadly combination with the enemy being blind(unless hyuga or sensor) and Zabuza can teach Jiraya the art of silent killing.
What Zabuza Has:
Incredible Durability(surviving all those weapons and still killing gato and getting hit with the water jutsu and surviving)
Incredible strength(wielding the enormous Beheader swords effortlessly, even with one hand)
Beheader Blade(a incredibly powerful blade that can never be broken and can kill in one strike)
Silent Killing/Hidden Mist Jutsu(The combination is deadly especially since Zabuza is unbeaten in Silent Killing)
Massive Chakra Reserves(Allow Zabuza to use a lot of jutsu, Visible Demon Shroud Chakra like Jinchurikis)
Fast Hand Signs(Allow for quick jutsu before the enemy can react, matching Kakashi)
Mobility(Zabuza has been shown to be fast and while holding a person with on hand he jumped to dodge a fuma)
Massive Suiton(Zabuza has shown the ability to use massive jutsu: Water Dragon Jutsu, Water Vortex Jutsu)
Speed(Enough to match Kakashi Hatake)
Water Prison Jutsu(Virtually inescapable technique which caught even Kakashi Hatake, water can be kept in scrolls)
Intelligence(While it is a 3/5 His use of water clones, and trapping Kakashi in a water prison speaks for itself)
Bad Qualities
Arrogance(Zabuza was arrogant towards the abilities of team 7, and it cost him, Jiraya can humble him)