I just got done finishing an MV-2F with lines in the graphics, so while it is still fresh I can post some stuff here for you to start checking, you can see my repair log here.
https://www.neo-geo.com/forums/index.php?threads/help-for-mv-2f-with-bram-issue.272773/
I'm definitely no expert, but if the cart is showing the same graphical errors in both slots it is likely not the C rom traces from the cart slot to the NEO-273.
Instead test continuity of pins for NEO-ZMC2 specifically 1-50, 79, and 80.
pin 79 ZMC to pin 44 NEO-B1 at E6
pin 80 ZMC to pin 45 NEO-B1 at E6
pin 1 ZMC to pin 46 NEO-B1 at E6
pin 2 ZMC to GROUND
pin 3 ZMC to pin 47 NEO-B1 at E6
pin 4 ZMC to pin 65 LSPC2 at D8
pin 5 ZMC to pin 147 LSPC2 at D8
pin 6 ZMC to pin 110 LSPC2 at D8
pin 7 ZMC to pin 109 LSPC2 at D8
pin 8 NO CONNECTION
pin 9 ZMC to pin 66 LSPC2 at D8
pin 10 ZMC to pin 53 NEO-B1 at E6
pin 11 ZMC to pin 54 NEO-B1 at E6
pin 12 ZMC to GROUND
pin 13 ZMC to pin 55 NEO-B1 at E6
pin 14 ZMC to pin 56 NEO-B1 at E6
pin 15 ZMC to pin 8 NEO-257 at J2
pin 16 ZMC to pin 11 NEO-257 at J2
pin 17 ZMC to pin 23 NEO-257 at J2
pin 18 ZMC to pin 27 NEO-257 at J2
pin 19 ZMC to pin 9 NEO-257 at J2
pin 20 ZMC to pin 12 NEO-257 at J2
pin 21 ZMC to pin 24 NEO-257 at J2
pin 22 ZMC to pin 28 NEO-257 at J2
pin 23 ZMC to GROUND
pin 24 ZMC to 40 pin NEO-257 at J2
pin 25 ZMC to 43 pin NEO-257 at J2
pin 26 ZMC to 55 pin NEO-257 at J2
pin 27 ZMC to 59 pin NEO-257 at J2
pin 28 ZMC to 41 pin NEO-257 at J2
pin 29 ZMC to 44 pin NEO-257 at J2
pin 30 ZMC to 56 pin NEO-257 at J2
pin 31 ZMC to 60 pin NEO-257 at J2
pin 32 ZMC to pin 8 NEO-257 at K2
pin 33 ZMC to VCC
pin 34 ZMC to pin 11 NEO-257 at K2
pin 35 ZMC to pin 23 NEO-257 at K2
pin 36 ZMC to pin 27 NEO-257 at K2
pin 37 ZMC to pin 9 NEO-257 at K2
pin 38 ZMC to pin 12 NEO-257 at K2
pin 39 ZMC to pin 24 NEO-257 at K2
pin 40 ZMC to pin 28 NEO-257 at K2
pin 41 ZMC to pin 40 NEO-257 at K2
pin 42 ZMC to GROUND
pin 43 ZMC to pin 43 NEO-257 at K2
pin 44 ZMC to pin 55 NEO-257 at K2
pin 45 ZMC to pin 59 NEO-257 at K2
pin 46 ZMC to pin 41 NEO-257 at K2
pin 47 ZMC to pin 44 NEO-257 at K2
pin 48 ZMC to pin 56 NEO-257 at K2
pin 49 ZMC to pin 60 NEO-257 at K2
pin 50 ZMC to pin 27 NEO-D0 at G11
Reference pages with pinouts
https://wiki.neogeodev.org/index.php?title=NEO-ZMC2
https://wiki.neogeodev.org/index.php?title=NEO-257
https://wiki.neogeodev.org/index.php?title=NEO-D0
https://wiki.neogeodev.org/index.php?title=NEO-B1
https://wiki.neogeodev.org/index.php?title=LSPC2-A2