3/3 mass Muta go through turrets pretty fast. I notice a lot of turret builder like to clump them together in lines, which means there's probably a big somewhere else, probe and find it.
I don't know why you're even worried about static defense, unless it's killing SCV's, if you're policing expansions with Muta or lings, and you have him confined to his base, its just a matter of time till he can no longer reinforce.
In this game if you're defending, and not attacking, you're losing - the only rationale behind spending a lot on static defense is so you can safely leave your base and attack, or try to kill the rush so you can counter before he reinforces - if he's just turtling, it's just a matter of time.
About the only reason I attack a main is to kill workers or critical buildings: Cybernetics Cores, Armories, etc., so he can't make Thors or Stalkers, and put him behind on upgrades - take out the Engineering bay and he can't make turrets.
Use Muta, take out a couple turrets, and fly off, check expos while they heal up, or make a bunch of queens at a base and use them to heal your Muta, then go do it again.
Once you have an area cleared, check back soon though, kill SCVs when they try to replace the turrets, that will run him out of minerals faster.
While you're doing that, or you do happen to get you're Mutas wiped out, which happens, you can hit him with little ling or Bane rushes to keep him running around and defending - but Muta are fast enough you can hit one side, fly a wide arc, clear around to the other side and hit that while his Marines are just getting to the first site.
But you can do all that while maintaining a decent sized ground out of range, protecting your base and/or expansions.
If he shows up with Marines, look for choke points, and try to get him to run through: if he's got a lot of buildings, and has to run between them, the marines have to go single file, and can't mass up to attack you - I've wasted mass marines with a middling batch of Muta because he had to squeeze them through a choke point, and there were never more than two or three at a time in firing range.
Take advantage of the Muta bounce attack: line your targets up, and you'll wear down whatever is behind whatever you're focusing fire on - i.e., if there's a pylon and cannons, line a pylon up behind a cannon, and by the time you kill the cannon, the pylons shields will be already gone, take out the pylon and the other cannons will be unpowered.
Same with lines of turrets, although you don't want to take on mass turrets with anything less than big batch of 3/3's, but once you do clear out a landing zone you can do a Nydus drop and use b/lings, roaches, etc. to clear out the turrets while you protect the worm with your Muta - you might have to put them on hold, the real downside to Muta is how aggressive they are, if you're not watching they'll fly into a bunch of turrets in a hearbeat.
I prefer to use Broods for this, with Muta support, keeping them out of turret range, but ready if he has Vikings, or to help thin out any Marines/Marauders that show up to kill the tunnel, tanks etc. Tanks are absolutely helpless against Muta, and I've ever seen a base where you can pack more than 2 or 3 turrets into a tank position.
There's a reason mass Muta is a popular build, even though they're less effective against Thor's or large batches of ranged infantry: you can really mess up a base, you can scout and get and get a good idea what he has and where they are, kill all his workers, take out his infrastructure and static defenses, and then finish him with ground - and as I say, large groups of 3/3's will rip though almost any static defense with proper micro, and half the time they give up after you killed all their workers anyway.