The Zerg campaign sure is weird. First mission, decent tutorial.
Next three, 2-5, you and the enemies are divided by impassible terrain. Thought zerg were about zerglings? Nah, it's mutalisks all the way! One mission (3 I think?) was needed a few grounds troops ferried over, but IIRC that was because the gas geyser ran out surprisingly quickly.
Then 5 is funny because it takes place entirely within a single unit. Alright flavor-wise, kinda tedious mechanics-wise, good plot progression though.
Anyway, I "died" (wasted too much gas, gave up and restarted) on 7, because suddenly there *are* enemies you can, you know... ZERGLING RUSH
They happen to be zerg, but still.
I went for mutalisks (flyers) again as trained (not just recently, but faint recollections of high school), not noticing the ramp to the west. The AI went *heavy* into hydralisks (ranged/AA shooters) who unburrowed to ambush my attack forces, repeatedly getting a few kills despite me withdrawing. It was pretty frustrating until I realized my mistake.
Starcraft 1
Edit: Turns out you're almost separated from the main force on 7 too, there's just a weak base to your west and a loooong corridor to the northeast! Man, it's really like they wanted to train Zerg players to spam mutalisks by default.