OP, question you need to ask yourself is what limitations do your current scopes have? Is it weight, size, reticle? If you are happy with all those things then what do you stand to gain from the ZCO or TT. I will say this, it sounds like you may have older Schmidt scopes with the older turrets, if that matters to you (turret feel and tactile feedback) then I'd say ZCO will be a step up and TT definitely a step up. That being said, I feel the new Schmidt DT II+ turrets are better than ZCO and I like the locking mechanism better as well as you can leave it on or off and the MTC is the best I've felt from Schmidt. TT has the best toolless zero/stop in the business, not sure if that matters but worth mentioning.
If you're looking for an upgrade to image quality, yes ZCO is better than Schmidt and yes TT is better than ZCO but we are talking fractions at this stage of the game and really it comes down to other factors like reticle, ergonomics and mechanics. All three scopes are going to be very forgiving in DOF, parallax and eyebox. If you own the PM II 5-25 then another factor is tunneling at low magnification, for this reason many consider the 5-25 to really be more like a 7-25 and FOV numbers reflect that. If FOV is going to be important to you, especially at the low end of magnification, the TT will be king and the ZCO will follow.
If you prefer a "lighter" scope then I think you can't beat the TT315M and to be honest I think the turrets are even "better" than on their 5-25, most likely due to the spacing at 6mrad per revolution. Another scope in the lighter weight category is the March 4.5-28x52, March really flies below the radar and has struggled some with their 8x erector designs, but the 4.5-28 (with 6.2x erector) solves a lot of those issues and is impressive optically and mechanically. If weight isn't so much a concern but "shorter" is, there is no better ultra short out there (optically) than the ZCO 4-20.
For me, at this stage it comes down to reticle, this is the thing you have to look at every time you look through the scope and I am very particular about reticle.
If you haven't seen ILya's video on high end tactical 56mm scopes you may want to check it out:
Agreed its fractions difference when it comes to high end scopes. And that reticle design is a bigger thing than trying to figure out which glass will be better. Also how many of use truly use the scopes in the high end ranges to the fullest per say? I would say not many. I have mid grade scopes, some high end and then the top tear S&B and ZCO. Unless I'm shooting past 1000-1500 yards the mid grade scopes can surprise you for sure. If you want a tank for a scope tho S&B, ZCO, TT are top notch with little difference optic quality wise. Mechanically as you stated can have differences because of preference.