Not recommended. The work of Waluga et al showed that combining Ephedrine/Caffeine with Yohimbine resulted in no greater fatloss than E/C alone, but reduced cardiac function AND raised blood pressure (at least in a group of obese women):
Cardiovascular effects of ephedrine, caffeine and yohimbine measured by thoracic electrical
bioimpedance in obese women.
Low caloric diet is a commonly accepted treatment in obesity. However, owing to moderate results, a pharmacological support has
been proposed. As some efficacious drugs activate overall sympathetic activity, they might modify functions of the cardiovascular
system. Three groups of subjects were studied: (1) nine obese women receiving only a standard hypocaloric diet; (2) nine obese
women receiving a standard hypocaloric diet and ephedrine (2 x 25 mg) with caffeine (2 x 200 mg); (3) nine obese women receiving a
standard hypocaloric diet and ephedrine (2 x 25 mg) with caffeine (2 x 200 mg) and yohimbine (2 x 5 mg). The cardiovascular state
was evaluated by thoracic electrical bioimpedance, automatic sphygmomanometry and continuous ECG recording. In each patient, the
haemodynamic study was performed twice: at rest, i.e. before treatment; and after 10 days of treatment. On the same days in each
patient, the haemodynamic tests were performed during physical exercises (handgrip stress and cycloergometer exercise). Caffeine and
ephedrine had no haemodynamic effect in resting patients. These two drugs led to an increase in ejection fraction during
cycloergometer exercise. Addition of yohimbine increased diastolic pressure and heart rate but decreased ejection fraction and stroke
index during rest. We also observed that addition of yohimbine decreased ejection fraction during the handgrip and cycloergometer
exercise and increased cardiac load during dynamic exercise. Pharmacological supplement of ephedrine and caffeine to a low caloric
diet modified the cardiovascular system weakly, but the addition of yohimbine to this regimen attenuated cardiac performance during
rest and handgrip and increased cardiac work during dynamic exercise.
It is also likely that ephedrine may counteract the lipolytic effects of yohimbine so you may get reduced fat-burning in the target area (that is assuming you believe that yohimbine can increase site-specific fat-burning). Best to take EITHER E/C or yohimbine. Maybe cycle them every 2 weeks??