Is the zeta DC-DC converter topology scalable to 50kW / hundreds of amps?
Is the (insert name) DC-DC converter topology scalable to (insert impressive power level)?


Yes.  OK, next question.

Oh, you meant reasonably scalable, didn't you?

The problem with the Ćuk, SEPIC &amp; zeta converters are that they carry considerable power in the filter capacitors, and they need multiple inductors.  So they may not scale as well as other options.

A 4-switch buck-boost should scale better than the above options, because you'll only need one inductor and one set of filter caps, at the expense of needing four switches.

I think if I were you I'd explore a multi-phase 4-switch (per bank) buck boost.  I know that if I were the one doing this there'd be a microcontroller controlling it, but whether you do that or seek out some controller chips that'll do the job for you is a strategic decision that depends on the team you have available.