Army-Firedawg
1000+ Head-Fier
Both L3 and L3Pro have single ended (3.5mm) and balanced (2.5mm) HO outputs, Line Out (dac output to use with external amp), Digital Out (to use as a transport to drive your external dac/amp), and you can use it as usb dac. The output is "quiet" keeping the hiss down to zero, but the output power is on a lower side since it's designed for IEMs/CIEMs, though you can still drive some less demanding full size. The only thing it's missing a touch swiping, you can only tap on a touch screen, though can use hw transport control buttons for scrolling in addition to touch keys.
Not really sure what do you mean by active input?
L3 indeed has a great synergy with Zeus/R.
As in I can plug my computer/phone into the L3 and then the L3 into my desktop setup