bah spoke too soon...
Ok, now instead of really loud hum it's just mildly annoying hum

observations:
if I turn the volume on the amp nearly completely down and then use the volume on the zsp1 it's very quiet but in order to reach listenable levels I have to have the amp at about 1.5 on the dial so there is a tad bit of hum.
If I pull the Left output to the amp, hum is totally resolved, dead silent with just the Right channel. If I pull just the Right, hum actually gets minimally worse.
If I turn the zsp1 off, it sounds perfect as the caps drain which lasts almost 45 seconds, during this time, no hum at all.
If I have the amp volume at 3 the hum is very audible, adjusting the volume on the zsp1 has no affect on the volume of the hum.
I'm going to try building another set of interconnects, I'll try them between the amp and the zsp1 since disconnecting either input has no effect on the hum.
oh well... the battle continues!