Drop top hats and tea for the zerg from orbit. Once they assimilate it, they too will become dapper and want nothing more than a nice cup of tea.
Also
Distribute supertea to humans in exchange for them adopting the dapper way
[1]
The zerg and humans are both batshit crazy right now. No-ones driving the zerg, and the humans are completely out of control.
Reveal our nuclear potato technology. Mimic recent potato-portal technology we witnessed, open portal to potato dimension.
[6]
You open a portal to the potato dimension.
YOU ARE THE CORRUPTED. YOU MUST PERISH. ONLY THE PURE MAY SURVIVEThe surviving potatoes are being shredded when they enter the portal.
Go beat up stragglers.
[3]
(Think as your weapon of a pair of Mass Effect Omniblades, but they can convert to shields if need be.)
Slice em up! A combat form has emerged from the burning nest. It's about the size of a sheep, has a massive amount of spines on its back, and is on fire.
Crap. That thing will try and porcupine-style roll at you, chop off its head before it gets the chance.Politely convince the Zerg to leave the planet, preferably after Erils has tried to make them gentlezerg.
[6]
If by polite, you mean intimidate them psionically until they obey you, then making them pack up and leave the planet, then yes, you ask them politely, and they do so. Unfortunately, now there's a zerg brood following you everywhere, and it's unruly as all hell.
The Protoss have joined in the multiversal war, and are supplying it with warfleets. They welcome the opportunity to talk to an alien race that isn't stupid to the point of oblivion, or one that is trying to kill them.