No way are they Tyranids. Its just got small relations...
lets compare the differences!
Mouths: Both have mouths
Food: Both eat
Death Animation: Both have death animations
Guns: Both have guns(Lolinfestedterrans)
Legs: Both have legs
Tank Unit: Both have tank units
Air: Zergs only have air units
Oxygen: Zergs can survive anywhere but Tyranids need a certain enviorment
SpaceTravelTechnology: Zergs can warp speed with slowass Overlords but Tyranids can steal War Ships
Time Travel: Zergs can cause time paradoxes, but tyranids make time loops
Build Time: Zerg build faster
Building Build Time: Zerg take longer, as Tyranids Have no buildings
Chance2Dodge: Tyranids have a higher chance to dodge
Magical Powers: Tyranids are dumb animals, but zerg can use psi(lol kerrigan)
Map Making: DoW2 sucks at map making. U cant make maps but in SC u can
Amount: Zerg can haz 400 lings! Tyranids can only have 40 worms
HP: Tyranids have more hp
Technology: Zerg have mastered warp speed on Overlords. Tyranids are behind but have guns
Jobs: Zerg are smarter when it comes to jobs, as they can harvest minerals! Tyranids cap the damn point
Food Cap: Zerg have 200. Tyranids have 100.
Resources: Tyranids gain more resources per second, but zerg gain more per return
Heroes: Zerg have like 8 heroes and Tyranids only have 3.
Anyways thats a comparisin. But i still like the guardian better. He looked just like a mutalisk, as they both looked like a wheel. but the Brood Lord looks like a Parachute(SC: Ghost Model???)