Tuner usually first cause you want a nice clean signal.. however, I've encountered some Wahs that suck tone. so if your tuner has a buffer built in, put it after. Itll help rejuvenate the signal and bring some high-end back into your signal.
did a quick looking.. the ST300 is Truebypass.. the ZW Wah is not True Bypass. It may be moddable to True Bypass. Does your budget allow for a buffer ? any other pedals on the board?
Sounds great. With EMGs or Active pickups you don't need a buffer at the start of the chain... If you like the tone/sound you're getting now then don't add a buffer anywhere.
If you want to experiment with it then add a buffer to the end of pedal signal chain as the last pedal before the cable that goes to the amp.