Can I jumper TIU input channels?

Yes, maybe.  Jumpering inputs is fine, IF you have enough power from the one Z1000 to run all the trains.  A better idea would be to get the $20 Radio Shack power for the TIU's Aux PWR and have your  two Z1000's feed two TIU Inputs each.

You can also plug the two Z1000 units into a fixed and variable channel each, no need for aux power for the TIU if you are powering fixed channel 1.   That way you have both bricks available, and you can use up to 100 watts on each variable channel.

Looking at your list of expected running equipment I suspect you are going to pop the breaker on the loop with 3 engines. Especially if you run lighted passenger cars, those things are power hogs. A Z-1000 brick can only output 5.5 Amps continuous at 18VAC. A long lighted passenger consist can use that all by itself.

A possible fix is to break the DCS loops into blocks about half the length of the passenger consist. Then connect each TIU fixed channel and it's brick powering alternating blocks. This spreads the load of each train across the 2 bricks.

We did four power districts.

And the transformer power input is jumpered from fixed to variable inputs.

One transformer handle powers both one fixed and one variable input side.

It's divided up so the variable ports never have much of a load on them, so for us it's not been a problem.