A picture of the drivetrain would really help, but i’m assuming since you said it is four motors in the shape of an octagon, you are using a weird form of an x-drive.
If you are, these links might help:
https://www.vexforum.com/t/x-drive-directional-drive-control-code-release-kind-of/82330/7
https://www.vexforum.com/t/x-drive-code/30081
The programming languages used might be a little different, but the math (the important part) should stay the same.