Taskmaster himself isn’t too hard a matchup, but the team matchup (task + beam + tron assist) is pretty terrible for Zero. It’s totally winnable with good assists on your team though. I will immediately tell you that Sentinel assist will be a huge help against that team.
For the most part, approaching from the ground is out of the question. Arrows + Beams is not going to make the short road easy. You’re gonna have to attack from the air, and Zero is very capable of this. If you have Sentinel assist, you can call Sentinel while super jumping and start moving forward. You take control of the airspace while Sentinel takes the heat on the ground. If they attack Sentinel, you’re in. If they attack Zero, you have time to block or counter and the Drones will be in play by the time you recover, probably across the screen giving you time to start an offense.
Projectile wars should not be fought on the ground unless you have a level 3 buster stocked. Shoot it just after calling Sentinel assist and the Buster shot should keep them occupied and beat most of their projectiles while Sentinel gets the drones active, then you can follow up with Hadangeki’s or start moving forward.
Because of Tron assist, you have to be extremely careful about attacking. The best time to initiate a mixup is when Sentinel assist is pinning them down, keeping them in blockstun long enough to mix them up with something. If they block it, call your other pinning assist (yes, preferably Dante,) and keep the pressure on with another mixup. As long as they are in blockstun they can’t call Tron.
The main thing you will have to worry about is the neutral game, when trying to get close to Taskmaster. If the opponent is catching on to Zero’s super jump height shenanigans, either by jumping himself to shoot arrows or using the upward arrows, you still have options. With Zero’s air H Hienkyaku, you can stay high enough in the air to avoid the upward arrows. If you know you’re not getting in close in that particular instance, then start shooting buster shots to pester them. Then when you land you have a bit of advantage. If Taskmaster takes to the skies, you can just run up to him from the ground and you have more control. Because he super jumped, you won’t have to deal with Tron assist until he lands.
In summary, don’t fight on the ground. Use assists in conjunction with air mobility options to establish better range, and only go offensive when it’s safe from Tron assist.
Check out my post on Trish. UPDATED "I don't even need my sword for such an easy fight" - UMvC3 Zero Matchup Thread