How well do you think Nixon's Vietnamization strategy worked?

It was not very successful.

His Vietnamization Plan was to allow an American withdrawal from Vietnam in circumstances which would allow the South Vietnamese to prevail. This in turn would avoid the humiliation of a defeat which meant that the US effort had been in vain.

Within two years of an American withdrawal South Vietnam fell to the communists. Moreover Cambodia fell to the Khmer Rouge and Laos to the Pathet Lao.