He clearly to clean out the bickering Cosmic Forces and build up his army from scratch not realizing that he is out of time! The Enemy is already on his doorstep and he is removing the defenses to replace them without having enough time to replace them!
He failed to consider that he had no time to face the threat coming for everyone for if he did consider that fact he could have simply just opened the way from the Maw and sent his Burning Legion-sized Army of Mawsworn to Azeroth to help weather the coming storm!
He should have grabbed all the Maldraxxi Allies, Forsworn, Venthyr Loyalists, Nathrezim and Mawsworn, built up his armies and sent them to defend Azeroth the moment the Enemy showed up!
It’s not like anyone ever encountered Mawsworn, Venthyr or Forsworn so them showing up to defend Azeroth from the 7th Cosmic Force the second it began invading would have endeared them to Azeroth!
Instead Zovaal wanted to wipe out all Cosmic Forces and try to build up an army from scratch without realizing he is out of time for that!