Zoom, viable bluff?

I like this play. OTT your draw is probably strong enough to call the raise.
Villain could raise with strong hands but he should have some bluffs too. River bricks and he checks. I believe he should quite often keep firing with some strong hands and bluffs. I would also pretty much exclude full houses because check calling this flop with 77,88,Q7,Q8 would be a bit weird.

I find it fine, but river bet size, what do you actually represent? Strong hands should be very big like pot size at least, and hands like Qx, should bet small like 25%-33% so that you get called with weaker hands (maybe A high, 56s and similar).

Strong hands should be very big like pot size at least,
Why?

His value range on flop is two pair+ maybe even AQ, KK, AA. bluffs some nut backdoors, some fd and oesd. The hands that call you on river are mostly slowplayed 77, 88, maybe AQ, KK, AA if he raises those on flop. 78s might call as well vs pot size bet because it has excellent blocker, it is paired board many draws missed, it is SB vs BB HU spot.
Some weak hands like 76s, 89s, 56s and similar if he has those in range might call as well. If you compare 50% bet size with pot size bet, he likely calls identical range or at least very similar because all draws are busted and you can't represent much when betting river. That is why i would bet big with strong hands like 88 for sure. 77 is questionable because he might call you river only with 77,88 (in the case he doesn't raise flop AQ, KK, AA) so i would rather bet smaller like 25% to make sure that hands like weak pairs, 78s call. If he checks river with hands like Q8, Q7 then it is even questionable if you can bet big with 88.

You can actually see how you can't represent much on this river, your value range is super narrow and you have quite many busted draws. Which is why the good option for villain would be to in fact call you light in this spot or even to c/r with blockers.
I think that on NL25 most of regulars wouldn't check any value hand on river, but would c/f with very high frequency on the river, so i would still bluff but would reduce size to 33% which is in my opinion max EV.