Wow a twin turret question. I'm in heaven :-D
I've been programming a 15TTF ZL35 for many years.
There is an option (not free) that gives automatic generation of balance cutting code in the FAPT/CAPS.
If you don't have that it's simple to align each tool then rough a part down in half the time using some simple code but generally to give full control it needs to be written long-hand. Do something like this... (material dia 100mm taking 5mm cuts)
Top Turret Program Bottom Turret Program
G00 X95.0 Z2.0 G00 X90.0 Z2.0
G1 Z-500.0 F0.4 G4 U0.5
X100.0 G1 Z-500.0 F0.4
G00 Z2.0 X95.0
X85.0 G00 Z2.0
Any M-code from M100 upwards tells the control to wait until it gets to the same M-code on the other turret. Then once they are aligned with the M-codes both turrets will go.
To do it in FAPT, program the part once with the real material stock size, generate the program then go back in and set the material size 10mm bigger then generate it again. Then manually merge the two programs taking alternating cuts. It's not that difficult and the time saved in rough machining makes up for it.
Or just pay and get the Balance Cutting Option :-)
It cost us about $10000 15 years ago. It paid for itself on the 1st job we did.