  The author showed that any homogeneous algebraic Diophantine equation of the
second order can be converted to a diagonal form using an integer
non-orthogonal transformation maintaining asymptotic behavior of the number of
its integer solutions. In this paper, we consider the transformation to the
diagonal form of a wider class of algebraic second-order Diophantine equations,
and also we consider the conditions for converting higher order algebraic
Diophantine equations to this form. The author found an asymptotic estimate for
the number of integer solutions of the diagonal Thue equation of odd degree
with an amount of variables greater than two, and also he got and asymptotic
estimates of the number of integer solutions of other types of diagonal
algebraic Diophantine equations.
