The Company namely M/s ABC properties have entered into an agreement with the principal owners for development and selling of the developed properties.
In turn they have assigned the same task to your in the form of an agreement with you which may be termed as a sub-lease too.
Since the principal owners have executed a power of attorney deed to yo directly (on the basis of recommendation by M/s ABC properties as their nominees), you will be developing and selling the properties to the desired purchasers keeping the principal owners in the picture and light.
There is no legal infirmity in it.
You can go ahead on the basis of agreed terms and conditions suiting best to the prevailing circumstances, that you have drawn with your own contractor i.e., M/s ABC properties.
However to be on the safer side you may refer the papers/documents to local advocate and take a second opinion from him before proceeding.