。
Balancing studying and club activities is hard.
Literal
Study [and-と] club-activities [obj-を] both-make-stand [nominalizer-のは] difficult.
両立させる ('to balance, to manage both') is the causative of 両立する ('two things coexist'). The causative form is used when the subject actively brings about the balance — 'make two things stand together.' 部活動 (clubs outside regular classes) is a big part of Japanese school culture and carries its own social weight.