iPod Touch CPU & GPU:
1st generation: ARM11 620 MHz (underclocked to 400 MHz, then 412 MHz)
2nd generation: ARM11 620 MHz (underclocked to 533 MHz)[1], with internal ARM7 core for Jazelle acceleration
2nd generation (Late 2009): ARM Cortex-A8 833 MHz (underclocked to 600 MHz)
1st/2nd generation: PowerVR MBX Lite[2]
2nd generation (Late 2009): PowerVR SGX
Zune HD CPU & GPU:
Nvidia Tegra APX 2600
One ARM11 and one ARM7 general processing cores[3][4]
Nvidia Tegra APX 2600
Several cores dedicated to 2D and 3D graphics, audio, video, HD decoding[3]
Zune HD graphics power > iPod Touch graphics power.
I can't wait for custom apps to start coming out officially. They're going to be sweet.