Yes the VF-S11 is only Sensorless.
It does have current and voltage limiting abilities that will prevent the drive from shutting off during any kind of overload, which as you said is essential
The drive has a feature which it calls "autotuning" which automatically detects the resistance, and inductance of the motor stator and makes a model of what it thinks will be the best V/Hz ratio for the motor. It works in the van but as I said it's not perfect because it isn't always right. It makes an educated guess and it's reasonable, but not ideal.
As JRoque said, what is needed is a variable torque response Regenerative Braking
system, so that when the brake pedal is pressed, the drive will serve negative torque proportional to the pressure on the pedal.
The acceleration is pretty good though. Sometimes the motor steps out and you can hear the motor hum. If the accelerator is lifted you can feel the acceleration come back and you know that you're in synchronization again. This is due to what I said before, it needs a speed sensor and true vector control, not just sensorless.
At the moment I have a pretty wild and crazy idea, which will probably never work out in the real world, but I'm thinking of trying it none the less, and that is to modify a VFD and try to sell it on ebay, As is with no warranties. Not sure who would be interested but I am seeing more and more people getting interested in Induction motors and high voltage in EVs. So you never know
As far as driving the Tri Zilla, Just about any VFD with true vector control should do the job, and long as the encoder is compatible. I don't have any specific recommendations because there are so many VFDs out there, it's hard to say which one is the best. Most VFDs will autotune, that is automatically set the parameters/programming. So I'd say look for one with autotuning and a compatible input. I'd also check for switching frequency compatibility, just to make sure it will work with what the Tril Zilla gate drivers are expecting. I would say, but I'm actually not sure what the original tri zilla switching frequency was supposed to be. Also the voltage, I'd imagine the tri zilla works from a relatively higher voltage. 240 volt 3 phase VFD will need 340 DC to turn on and run so the Tri Zilla should be compatible with that
Also I'll be happy to answer any more questions you may have about VFDs and induction motors in EVs