Seraphim Needed's solution is great, but something else to really make this easier on yourself is your specific loadout:
Aura burst and instant hero are a must for mostly all class C suits. small giant is a definately a highly recommended pick for these two missions with the ball and zaku tank. the loadout that seems the most effective for the Ball I've come upon is like this:
Biocomputer, Aura Burst, Armor Gain
Instant Hero, High Tension (the ball's hyper-SP attack is quite solid, and with this setup you'll be spamming it like crazy), Beginner's Faux Pas (could swap in small giant, although probalby unnecessary)
spam SP, then with biocomputer ABUSE THE BALL's DASH ATTACK to roll all over enemies faces and regain sp super fast. Launch another SP with the meter build-up you get from dashing/attacking with aura burst, regaining armor from armor gain attachment. Once you power down a field after conquering it, just dash through all the clusters of enemies to have aura burst mop them up and rake in the kills. safe and highly effective. combined with the atk bonuses from instant hero and beginners' faux pas you will be doing a surprisingly devastating amount of damage with your very powerful dash roll, x-string, and hyper-SP spam.
I would have posted this in the comments section of the previous post, but it's so old I'm not sure it'd be editted in and lets face it: most people probably dont read comments.