Complex sentence: Dlouhý has been part of two long-term doubles partnerships, first with countryman and coach Pavel Vízner and actively with Leander Paes, in which he has reached numerous grand slam finals with each.
Split into simpler sentences: Dlouhý has been part of two long-term doubles partnerships, first with countryman and coach Pavel Vízner and actively with Leander Paes. He has reached numerous grand slam finals with each.