How to solve a system of 3 or more ODEs having interdependent independent variables as independent variables of the dependent variable on the same derivative ?

Suppose, t1 = t2^2;

dX/dt1 = z+4;

dY/dt1 = 2*z+1;

dX/dt2 = 2+3*z;

dY/dt2 = 3+(z^2);

(May be the question doesn't make any sense to many, but still if you get the question, try to solve!)