So to the OP I think you need to consolidate a budget and weight class. The optics you listed after mentioning ZCO aren't in the same realm as ZCO. As far as Alpha/Tier 1 Glass quality is concerned TT/ZCO/S&B/ZP5 > Gen III Razor/7-35ATACR/Kahles > ATACR/AMG/Gen II Razor, MK5, XTRIII, Cronus, XRSIII, etc. I truthfully dunno where march sits in that lineup. I'm guessing between the GenIII/ATACR and the Tier 1 stuff.
Weight and budget are something you need to just basically set for yourself and that will narrow quite a bit from the choices.
Like Lance, I've spent a stupid amount of money chasing glass. This day in age you can have really nice glass for 1500-2000. Of those that you mentioned the ZCO is the best. But it's hard to just throw out a lot of different optics that truthfully have different purposes and saying pick one.
Which brings me to my question. What's the purpose of the rifle? Are you going to be lugging it around on back country? Lugging it around hunting? If so I think TT315M or March are your options for alpha glass and moderately lightweight. Is this a rifle you're going to just run in competition and go to the range with? Well then of what you listed the ZCO527 is going to be hands down the best choice you've listed. I will say if you don't want to spend $4000 the ZP5 and Gen III Razor are really close to ZCO in IQ. People will **** me for that but I've sat for hours with my ZP5 next to the ZCO 527 and as the ZP5 has done for years it's trading blows with TT and ZCO. Astonishingly the Gen III when I took it out this past weekend next to my ZP5 had better contrast to my eyes. ZP5 still beat it out in edge to edge clarity but they were pretty much equal in DOF and resolution. Where ZCO and TT do differentiate themselves besides nearly perfect glass. Is that their fit and finish is just superb. TT has the best turrets money can buy and if you talk to someone that has felt them they'll say there is nothing like them. ZCO has really nice turrets, I like them alright though personally prefer Kahles elevation turrets to theirs. Gen III turrets are super underwhelming and there seems to be some sample variance. ZP5 turrets at least revised (white box) are pretty nice. Not the best but I quite like them.