Shareholding & Acquisition of share of one pvt. co by another co.

Company A having 3 shareholders in head of J (50% shares), SS (1% Shares) & ZZ (49%). Now ZZ want to sell her shares then first preference will go to J & SS respectively. In case both shareholders (J & SS) refused to buy her 49% shares then she will go for its sale to external party. In this case, another Company B having 3 shareholders in head of J (20% shares), SS (60% shares) and SD (20%) wanted to purchase 49% shares of ZZ of Company A. However, J & SS are also existing shareholders of Company B. Now questions are:- 1. Who will assess shares value of ZZ (49%) of Company A for sale & its criteria? 2. Can Company B purchase (as whole) of 49% of ZZ (Company A)? If yes then company B will be owner of 49% shares or individually shares holder of Company B. Also suggest its implication on each shareholders of both companies. 3. If 2 point is applicable that is also called as merger then who will take decision on part of Company A (50% shareholder of Company A or 100 % shareholder of Company B). 4. If 2 point is applicable then what will happened to profit of Company A (about 50% shares profit which Company B owns) 5. Also suggest best solution by reviewing all 4 points if ZZ (49% of Company A) want to sell her shares and advantage goes to either Company B as whole or Shareholder of Company B. Pls note J is managing director of Company A and SS is managing director of Company B. Thanks Rohit