[ficofico]

soyou can not really compare cross platform like that

yes, but you can compare slrgear VFAtarget and watch your self that zeiss 24-70 at 24 f8 have really more resolution at lest 90% of the frame than zuiko 12-40 at 12 f8 if you resize both images at 3000 px 

 

zeiss

https://dl.dropboxusercontent.com/u/8602032/test/zeiss%2024%20f8.jpg

 

zuiko

https://dl.dropboxusercontent.com/u/8602032/test/zuiko%20f8.jpg

 

download, open in photoshop, bucubic resize heigh=3000, save quality=11

 

 

It's obvious that zeiss 24-70 f4 it's not able to match the 36 megapixel sensor, but it's quite obvious that, resolution wise, combo a7r + 24-70 f4 it's better that 16 megapixel sensor + zuiko 12-40 f2,8.... see your self or try to replicate download the file