Well, I was trying to troubleshoot (not yet finished; but here are the results so far).

I think the problem may lie in any one (or all) of these areas:

1. Zwift not reading the power correctly (that PerfPRO is transmitting);
2. PerfPRO not transmitting the power correctly;
3. Some of the USB ant+ sticks...

Anyway, I know that PerfPRO is transmitting correctly, because on an app on my phone, my phone is getting the correct readings.
The USB ant+ sticks are also working (I changed them into different combinations).

Zwift and PerfPRO are not fighting for control over the CT, methinks; I assign the CT to either Zwift OR PerfPRO, and to whom I assigned it is the one that controls it (in this case, I want PerfPRO to control). Besides, in the options of pairing Zwift with either the CT or the simulated power via ANT+, I already chose the ANT+ option (and if I run PerfPRO first, then the CT option is actually not available to Zwift -- first come, first served, I guess!).

Right now, I can't properly run the two together (unless I end up fluctuating between 0 and 2500+ watts - sure to get the ire of Zwifters everywhere; I'm sure the green jersery would be out of reach of even Kittel and Cavendish, haha)

I don't have a power meter, so cannot further cross check.

My next plan of attack (maybe later in the afternoon or so), is to switch USB hubs. Maybe three of them together in one hub is no good.

At least I know that PerfPro is transmitting correctly. And that the ANT+ sticks are fine. Right now, boils down to either Zwift not reading what PerfPRO is transmitting, or perhaps three ANT+ sticks in the same hub are causing issues.