Rewrite multiple second order differential equation to solve with Runge-kutta 4

I need help with rewriting multiple second order differential equations so that I can solve them with Runge-kutta 4.

My equations look like this

and I have the starting values of c=0.0084, z0=1.78, m=0.112, xdot=cos(27) and zdot=sin(27).

I've tried rewriting these equations to systems of first order equation but I cant quite figure it out.

[James Tursa]

What have you done so far? What specific problems are you having with your code?