Okay guys, this worked for me and may work for you. when making the combo's for this achievement, make sure to apply them in the correct order for each card.
for example:if you make zap 'n shine, first put up the floor buffer, then the stun rod.
The other combos are:
Lightning Gun = BFG + Stun Rod
Reaper = Scythe + Katana
Impact Blaster = Impact Hammer + BFG
Sterilizer = Chemicals + Syringe Gun
Shocker = Defibrillator + Medical Trays.
Laser Sword = Gems + Flash Light
Laser Gun = Laser Sword + Lightning Gun
I included the laser sword combo card because it is necessary to make.
One last thing that i also did: Don't Skip the weapon combo scenes!
Let me know if this helped at all.