The no damage taken is usually a pretty dead giveaway that they've got something shady going on.
The first fight - 56 hits. There are 4 ways to heavy Zola to keep his charges down; use a relic, parry him (will take damage without perfect block, and Kingpin has to reparry anyway), counter a heavy (will take damage baiting it) or punish an SP2 (which comes with guaranteed damage). The only way to keep from getting put to sleep and getting wrecked, without taking damage and with that hit count, would require like 4 relics - that's not happening. There is no way to take zero damage against Zola with that many hits and in that time frame without a champ that can both parry non-contact and get good perfect block RNG.
Report and move on. Kabam will be able to see if they're using third-party software.
Hits received includes blocked hits, but unless they had 33 & 27 perfect blocks it's impossible to not take any damage. That number would have to be very low or 0 for a no damage taken (and even low numbers are still unlikely but sunspot gets perfect block on parries if the opponent is incinerated).
Kingpin even with his reduced regen rate will regen a lot from willpower. I could see it happen maybe, but it is a little unlikely. Just as a reminder, Kingpin has the unstoppable with the heavy so he could potentially just tank the hit, regen from willpower and keep charges down that way. The second Arnim fight is much more likely as you just get to a sp3 and regen your entire health bar.
Even if he healed the damage back, it would show there was damage. No damage taken means that he was every time he was hit (33 times) even in block, it did 0 damage. Which is not possible for a 6 star kingpin. The match is possible as you said with full health, but that's not what "No damage taken" means.
Pure skills