I just drone scout, and if I scout a pool thats finishing up or finished before the 2:10 ish mark, I'll 15 pool instead of 15 hatch which makes holding early pools very manageable. You still have to be careful and not lose drones easily but once you know its coming thats easy to do.
If you search for something like 'belial zvz holding a 6 pool team liquid' that should give you a really nice guide to learn from.
I started wondering if anyone alters their build once they see the 6 pool on the way
no don't alter your build at all. If you wanna go 14 pool 16 hatch then God damn it plant down that hatch at 16, try and ignore all the distracting "your drones are under attack". It's just blizzards way of trying to stop you from doing your build.
Plan to 15 hatch. If he goes 6pool, pull drones and a click when you think you can get a surround on the lings. It comes down to micro, if you survive with ~8-10 drones and kill the initial lings you're ahead. If you scout his 6pool earlier, then just make a pool ASAP because you don't really need the hatch's extra larva if you only have 8-10 drones, and you get some lings out faster if he transitions into a round 2.
14 pool can beat 6 and 7 pools as long as you see it coming and can prepare by making lings and one or more spines to defend. Just remember hold it off, you win
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