Complex sentence: The projected tower had been a subject of some controversy, attracting criticism from both those who did not believe that it was feasible and those who objected on artistic grounds, whose objections were an expression of a longstanding debate about the relationship between architecture and engineering.
Split into simpler sentences: The projected tower had been a subject of some controversy, attracting criticism both from those who did not believe that it was feasible and also from those who objected on artistic grounds. Their objections were an expression of a longstanding debate about the relationship between architecture and engineering.