Most of the chips based on mobile soc also have a GPU.
I'd imagine the rpi0w gpu has enough gpu performance to make it worth thinking about. Last time I checked its all ASM based (don't think theres an OpenCL port to the broadcom society) but its 12+ cores, dedicated read caches etc.
The nice thing of course, is that you can write the app for just the CPU on a rpi0w board and then offload calculations to the gpu if you need more speed.