What you should do is obvious imo. Retreat, on a path leading it into your next enemy. And if it both survives and isn't time-limited, continue doing that.
Obviously positioning yourself and your hero unit on another path, so you are safe and jsut have to risk/sacrifice zerglings.
ps: mary-tan, that amount of white somehow burns my eyes despite just having come from reading bright white manga pages D; (probably because eyes are normalized when there's plenty, but here it's so uneven and rare they aren't?)