I replaced the old pups in my Ibanez Talman with two Guitarheads 4-head HBs. I want to split both pups with one DPDT switch. Has a three way strat switch. I tried to copy the wiring from the old pups except for the extra wires.
1 - Where are the white wires? Do these pickups have white wires? Were they intended to go to the split switch with the red ones? If there's no white wires, or they are going with the reds, then your split will work as drawn, but...
2 - Assuming these two pickups are exactly the same, you'll be splitting to the same coils on both. This will not be humcancelling. There's a couple ways to fix that, depending on your answer re: the white wires.
3 -This is obviously an incomplete schematic, meant to illustrate your idea for the split switch, but as you've got it drawn, the (3-way?) blade switch is set to have both pickups on in two positions and nothing in the third. That can't be what you intended, can it?
Unless you know the wiring color scheme for the particular pickups, we don't know which coils, N or S, you'll be selecting. Ash's point was, it's going to be the same coil on both (assuming they're both the same pups), which won't be hum-cancelling.
To get hum-cancelling, you need one N coil combined with one S coil. If the red and white are the series junction for these pickups, you can get the opposite coils by wiring one of the two "inside out". Wolf explains how to do this on his website.
But if these aren't SD pickups, do you know what they are? If not, there's no guarantee that the red/white pair is the series junction you need for the coil split. Some testing before wiring is your best bet if you're not sure of the wire colors.
You don't have to go through all the trouble to wire it inside out. Not that it's all that difficult, but...
Pick a pickup. On its side of the split switch remove the wire going to the back of the volume pot and put that pickup's black wire on that lug instead. That black wire still needs to get to the blade switch as well. Doesn't matter which switch it hits "first".