How to beat a Zerg that goes for a Zergling/Baneling/Mutalisk mix?

Watch my replay here. (Scroll down, look for "Save file to your PC: click here" in the box)

I did Cons Shells against Banelings, Tanks against Zerglings and Marines/AA/Vikings against Mutas.
Furthermore I also upgraded their armor and then their firepower from the Engineering Bay.

Tried an harass with Banshees but that failed, so did my push against his natural...
I didn't choose to drop because his zerglings/overlords/mutas would see it coming.

That didn't work out well! What did I do wrong?

The problem were the Mutas, I couldn't take those down. Should I have gone more Vikings instead?

Before I even watch any further than 7:30 mins

He already had an expansion, 10 more workers and was scouting the map, seeing you hadn't expanded yourself.

At that time, you had 8 Marines + 1 Marauder, he only had 1 Zergling + 2 Queens.

If he wants to progress into Banelings and Mutalisks as fast as possible, he's going to need a lot of gas to built the buildings required and the units, he needs expansions to pay for it.

So your most important failure is probably not having map control, thus not spotting an unguarded expansion or simply pushing while he was still weak.

Watching further (10 min mark):

You've gained two Tanks, some Marines and a Marauder. But still have only half of his amount of workers, which means he's simply outmacroing you on resources, thus capable of teching quicker and getting more units.

Within 2 minutes, he gained 20 Zerglings and 20 Drones. The only noticeable tech he has at this point is the Banelings Nest and an Evolution Chamber, upgrading his units.

Meanwhile, you upgraded to make Tanks with Siege modes, added a Techlab to your Airport (thus not making units from it) and was upgrading Armor in your Engineering Bay.

A better approach would have been to have out a Medivac as soon as possible and see if you could annoy the Zerg player. This has the advantage that you get to see what he's doing and hopefully take out some Drones in the process. Instead you leave him alone, outmacroing you.

By 15 mins you decide to attack

While he doubled his amount of Zerglings, got his third expansion up and running, had Overlords checking all other possible expansion areas and making sure you couldn't built there by placing creep. He even got out 15 Muta's.

You went to his base with the banshees (hence you made the Techlab earlier), but hadn't noticed he already had an Overseer. He already had that one at the 10 minute mark, had you spotted it back then, you could have skipped Banshees altogether.

In the meantime, you didn't get an expansion nor did you significantly increase your army to match his. You have been protecting your base against air attacks, but those Missile Turrets are 100 minerals a piece and can't be moved. Making Marines with a Medivac would have suited you better, especially on such a large map.

By the 18 minute mark

You decide to pull out, which was probably the worst moment: he just started to transform his Zerglings into Banelings (17). Together with his 27(!) Muta's, there was nothing you could do.

My conclusion

Yes, you made all the right counter units, but you didn't make enough of them to stop him. What should you have done differently? Be more aggressive, make sure you're ahead in something (either units or resources) while not being too far behind on others.

Yes, you teched up, but if you have only have 50% of his units and 20% of his resources, those upgrades won't help you one bit!

If he has a lot of Mutas go with Thors. Unless your opponent knows how to box the Mutas, you will annihilate them. Thors destroy mass Mutas because of their splash damage and because it takes a while for Mutas to kill them.