The whole thing about ZIP is that it works on a completely different metabolic than stimulents and thta's part of what makes it superior. People like to "feel" that jolt from ephedra or caffeine or yohimbe, but that does not directly burn fat. The thyroid directly burns fat.
You can't elevate body temperature with stimulents unless you ant to take something like clen or DNP. But ZIP has elevated the temperature of hypothyroid people. (See reviews on the PF site)
The only advantage to stimulents is that they supress appitite and they get you amped so you can work arder during a workout. If that works for you, the combination of Thermorexin and ZIP would most definetely kick ass without getting you any more wired than the Thermo alone.
As a matter of fact, if you can get some old Ripped Fuel with ephedra and take it with ZIP, that would be very intense, but go with a half dosage to test the waters. It may be TOO intense. (Very much like clen as a matter of fact).