  Context. Planets are thought to form inside weakly ionized regions of
protoplanetary disks, where turbulence creates ideal conditions for solid
growth. However, the nature of this turbulence is still uncertain. In this
zone, vertical shear instability (VSI) can operate, inducing a low level of gas
turbulence and large-scale motions. Resolving kinematic signatures of VSI may
reveal the origin of turbulence in planet-forming disks. However, an
exploration of kinematic signatures of the interplay between VSI and forming
planets is needed for a correct interpretation of radio interferometric
observations. Robust detection of VSI would lead to a deeper understanding of
the impact of gas turbulence on planet formation. Aims. The goal of this study
is to explore the effect of VSI on the disk substructures triggered by an
embedded massive planet. We focus on the impact of this interplay on CO
kinematic observations with ALMA. Methods. We conduct global 3D hydrodynamical
simulations of VSI-unstable disks with and without embedded massive planets,
exploring Saturn- and Jupiter-mass cases. We study the effect of planets on the
VSI gas dynamics, comparing with viscous disks. Post-processing the simulations
with a radiative transfer code, we examine the kinematic signatures expected in
CO molecular line emission, varying disk inclination. Further, we simulate ALMA
high-resolution observations to test the observability of VSI and planetary
signatures. Results. The embedded planet dampens the VSI along a radial region,
most effective at the disk midplane. For the Saturn case, the VSI modes are
distorted by the planet's spirals producing mixed kinematic signatures. For the
Jupiter case, the planet's influence dominates the disk gas kinematics.
Conclusions. The presence of massive embedded planets can weaken the VSI
large-scale gas flows, limiting its observability in CO kinematic observations.
