Gojart Demiri

Yes.  I have done the exact thing and it works fine.
 
You're buying 2 of the exact same thing.  The 2nd kit is as similar to the 1st kit as the 2 sticks are to each other in each kit.  Meaning, all 4 sticks are as similar as possible.

If you buy both kits from the same place it's most likely fine.

is this ram compatible with my motherboard : ASUS ROG MAXIMUS FORMULA XII 
64GB (4x16GB) G.Skill Trident Z RGB DDR4-3600 CL17 (17-19-19-39) DIMM RAM Kit.

thank you very much for your help so now its on me to decide

Also depends on the radiator thickness. 
 
The A700's 420 rad would probably have to be a standard 27mm thick, because with a fan it would extend towards whatever GPU you're using (examples of similar builds can be found on PC-O11D's). 
 
The Define 7 XL doesnt have rad thicknesses listed, but based on past Define R6 builds I've seen it's likely you could do push/pull on front and top at least with slim rads, possibly one of them being a thicker variant (38mm, 55mm, 60mm)

Please don't post multiple times about same thing:
 

"Yes" as in it depends on all the other stuff you're going to be putting into it. In an empty case without fans and rads it will fit, but the only way to know of it will fit with all the stuff you want to put in it is to try it, unless you can find someone with that EXACT same build you're trying to accomplish.