The phrase "are employed simultaneously" is correct and usable in written English.
It can be used when discussing multiple methods, techniques, or processes that are used at the same time.
Example: "In this experiment, various techniques are employed simultaneously to achieve more accurate results."
Alternatives: "are used at the same time" or "are utilized concurrently."
Two sensors, a global position sensor and medium derived positional information, are employed simultaneously.
Superior results are obtained when the three proposed FRT controllers are employed simultaneously.
When both modifications are employed simultaneously, their effects essentially compensate each other.
Several diagnostic tools, a CMOS digital single-lens reflex camera, current and voltage probe, are employed simultaneously to confirm the occurrence of pinching in the device.
Two common types of shortcuts used for this purpose are location breadcrumbs and down-to-child/up-to-parent links; frequently both are employed simultaneously.
Two image-intensified, high-speed CMOS cameras are employed simultaneously, in order to visualize the highly unsteady combustion process in terms of OH∗ radicals and soot, respectively, with relatively high temporal resolution and data throughput.
Traditional pressure scanning method, PSI, was employed simultaneously during tests.
Chemisorption and physisorption can be employed simultaneously in a complementary binding process.
For six months in 2012, Abedin was employed simultaneously by the State Department, the Clinton Foundation, Clinton's personal office and a private consulting firm connected to the Clintons.
The fact that the administrators were employed simultaneously by the district and by the social services agency was apparently unknown to auditors and district officials.
Her apprentice years in New York theatre included the feat of once being employed simultaneously in shows on Broadway and in Connecticut, her exit in the former allowing time to catch a train to make the later curtain for the latter.
