Ah the scourge invasion how I love thee! (Spoilers I killed Khadgar!)
So I started by going to Darnassus then using the Hellfire Peninsula Portal before I became a zombie.
There my first stop was honor hold: https://prnt.sc/vkas78
After Honor Hold I went to Thrallmar… Because FOR THE SCOURGE ALLIANCE!: https://prnt.sc/vkaur8
I then traveled in Zangramarsh and spread some fun there too: https://prnt.sc/vkayb8
Finally to Shattrath: https://prnt.sc/vkazu4
There I infected trainees who quicky turned into zombies: https://prnt.sc/vkb0tu
I couldn’t Directly Kill Khadgar https://prnt.sc/vkb16n However by training some zombies he too became my servant: https://prnt.sc/vkb1za
Dead Khadgar: https://prnt.sc/vkb26d
Interestingly Enough I could take the Horde Portal to Ogrimar: https://prnt.sc/vkb3ro
However Upon taking it my zombie failed and and reverted back to human: https://prnt.sc/vkb42u
Update: I created a self replicating army: https://prnt.sc/vkcr53