оптимальная работа busin.

[Daffodil3]

Помогите пож-та со второй частью предложения:
И хотя результаты его (специалиста по маркетингу) работы гораздо сложнее оценить, чем, к примеру, результаты работы менеджера по сбыту, именно от него и его профессионализма зависит оптимальная работа и прибыль всей компании в дальнейшем.

Мой вариант:
And though the results of his/her work are much more difficult to evaluate than the results of sales managers’ it is the marketing specialist and his/her professionalism ??????????????.

ЗС

[%&$]

Off-hand:
it is his professional competence/skills [in the logn run/final analysis] that guide[s] the company through the best way of doing business and onto its value in the future.

[Kirsha]

Although the marketing specialist's performance is much more difficult to assess than that of the sales manager, it is his/her skill that enables the company to work/ function/ do business efffectively.

[%&$]

specialist's - лучше marketing team/staff/people or marketing professionals
specialist - в большинстве случае либо армейский специалист, либо специализированная компания. )
Missed sth and stand corrected:
onto [INCREASING/ENHANCING] its value in the future.