The next flash freeze strikes at a very opportune moment- just as a Protoss zealot force assaults your base. Take advantage of this opportunity to kill them and you may find you have time to also assault the base of the nearest communications spire. If not, don't worry- use the time to instead build up more units to attack with.
The first communication spire is directly to the North of your main base, and such a short distance away that it is very easy to make quick attack runs. Happily, there is also an Ursadon Matriarch a short distance further North from that, so once you finish off the base you may as well also head along a bit further and swipe that DNA. The defenses here are relatively light- zealots, stalkers, a cannon or two, and that’s it. It’s the least dangerous of the Protoss camps on the map, though, so be aware that it’s not an indicator of how easy the rest of the mission is going to be.
When you destroy the spire, Sarah will take notice of the nearby minerals and have Eisha air-drop a new hatchery into place- taking advantage of the added resources is key to completing the mission in anything even slightly resembling a timely manner. The hatchery also comes with a creeper colony, and you would do well to also swipe the existing one from the outpost you rescued to defend it and leave units to protect the old location.
As you progress, the durations of the flash freezes will shorten, making it more difficult to take advantage of the frozen state of the Protoss. Keep your eye on the timer at the top of the screen- a good rule is to pull out of the attack with 10 seconds left in the freeze, and then burrow somewhere nearby- this will let you stay hidden, as the Protoss here have no observers and it should be very simple to stay out of sight range of enemy cannon. There are several Protoss enclaves around the map, built on structures that are part of the ground itself- when you see Protoss buildings that you cannot attack, be wary because your units are entering a dangerous area.
Each of these emplacements, which are akin to some kind of bridge, has at least one colossus on it, putting zerglings at very high risk when a flash freeze is not going on, as well as at least two cannon supported by a pylon. If you’re reaching for the Ice Breaker or Storm Chaser achievements, this is a key place to use roaches- or, if you have them by now, other higher-value assault units. Virtually anything is more suited to being backed by queens than zerglings are, and colossi and cannons will make quick work of massed light units. While stalkers have a slight advantage against armored units, there aren’t enough of them present in any location to make that a large concern and queens will greatly blunt any incoming damage anyways.
