I'm seeing huge cpu & memory usage on my windows 64bit system with both the daemon & QT with the latest version - 20%+ cpu & well over 1.2gb mem usage. The QT is almost completely unresponsive sometimes, showing the dreaded "not responding" message most of the time. My linux systems don't suffer from this - any ideas?
If your Linux is good, then I'm thinking it's hit & miss as to what systems it eats up. On both Debian 8.7 & Debian 9 I've got it using 1.9GB mem and as much as 50% CPU usage while running (not initiating). 
Win10 x64, ZET QT 11.2.3 showing cpu down to near zero after a few minutes of being open but ram usage staying at 1.6GB.