If my calculations are correct...

[Loupeitak]

After weeks of hatching eggs for the right nature, IV's and Hidden Power i'm finally gonna EV train.
I was gonna use vitamins on the stats i'm gonna use leaving me with 310 EV's.

By attaching a Macho Brace would divide the EV's by two giving me to train just 155 EV's.

And i also have a Zigzagoon with Pokerus in the PC. If my pokemon get it it would divide the EV training by two.

Now here's the problem. 155 / 2 = 77.5
Is it possible to get 0.5 battles ?!?!?! (Taking in count that each battle = 1 EV

[Don't Run With Scizors]

Two of those effort points won't contribute to any stat at all, so you effectively only have to train for 308 points. 308 / 4 = 77.

[TeleFox]

Also, if anyone needs to know:
If you've got Pokérus and the Macho Brace, but you need 2 EPs rather than 4/8/12, just remove the brace for one battle vs. a 1pt opponent.