diff --git a/pandas/_libs/tslibs/tzconversion.pxd b/pandas/_libs/tslibs/tzconversion.pxd
index 190205d9c3c44..7f445d7549f45 100644
--- a/pandas/_libs/tslibs/tzconversion.pxd
+++ b/pandas/_libs/tslibs/tzconversion.pxd
@@ -3,4 +3,4 @@ from numpy cimport int64_t
 
 
 cdef int64_t tz_convert_utc_to_tzlocal(int64_t utc_val, tzinfo tz, bint* fold=*)
-cpdef int64_t tz_convert_single(int64_t val, object tz1, object tz2)
+cpdef int64_t tz_convert_single(int64_t val, tzinfo tz1, tzinfo tz2)
diff --git a/pandas/_libs/tslibs/tzconversion.pyx b/pandas/_libs/tslibs/tzconversion.pyx
index 030549f2528ed..ffd076d0608f2 100644
--- a/pandas/_libs/tslibs/tzconversion.pyx
+++ b/pandas/_libs/tslibs/tzconversion.pyx
@@ -28,7 +28,7 @@ from pandas._libs.tslibs.timezones cimport (
 # TODO: cdef scalar version to call from convert_str_to_tsobject
 @cython.boundscheck(False)
 @cython.wraparound(False)
-def tz_localize_to_utc(ndarray[int64_t] vals, object tz, object ambiguous=None,
+def tz_localize_to_utc(ndarray[int64_t] vals, tzinfo tz, object ambiguous=None,
                        object nonexistent=None):
     """
     Localize tzinfo-naive i8 to given time zone (using pytz). If
@@ -329,7 +329,7 @@ cdef int64_t tz_convert_utc_to_tzlocal(int64_t utc_val, tzinfo tz, bint* fold=NU
     return _tz_convert_tzlocal_utc(utc_val, tz, to_utc=False, fold=fold)
 
 
-cpdef int64_t tz_convert_single(int64_t val, object tz1, object tz2):
+cpdef int64_t tz_convert_single(int64_t val, tzinfo tz1, tzinfo tz2):
     """
     Convert the val (in i8) from timezone1 to timezone2
 
@@ -338,18 +338,15 @@ cpdef int64_t tz_convert_single(int64_t val, object tz1, object tz2):
     Parameters
     ----------
     val : int64
-    tz1 : string / timezone object
-    tz2 : string / timezone object
+    tz1 : tzinfo
+    tz2 : tzinfo
 
     Returns
     -------
     converted: int64
     """
     cdef:
-        int64_t[:] deltas
-        Py_ssize_t pos
-        int64_t v, offset, utc_date
-        npy_datetimestruct dts
+        int64_t utc_date
         int64_t arr[1]
 
     # See GH#17734 We should always be converting either from UTC or to UTC
@@ -381,17 +378,15 @@ cpdef int64_t tz_convert_single(int64_t val, object tz1, object tz2):
         return _tz_convert_dst(arr, tz2, to_utc=False)[0]
 
 
-@cython.boundscheck(False)
-@cython.wraparound(False)
-def tz_convert(int64_t[:] vals, object tz1, object tz2):
+def tz_convert(int64_t[:] vals, tzinfo tz1, tzinfo tz2):
     """
     Convert the values (in i8) from timezone1 to timezone2
 
     Parameters
     ----------
     vals : int64 ndarray
-    tz1 : string / timezone object
-    tz2 : string / timezone object
+    tz1 : tzinfo
+    tz2 : tzinfo
 
     Returns
     -------
@@ -411,15 +406,15 @@ def tz_convert(int64_t[:] vals, object tz1, object tz2):
 
 @cython.boundscheck(False)
 @cython.wraparound(False)
-cdef int64_t[:] _tz_convert_one_way(int64_t[:] vals, object tz, bint to_utc):
+cdef int64_t[:] _tz_convert_one_way(int64_t[:] vals, tzinfo tz, bint to_utc):
     """
     Convert the given values (in i8) either to UTC or from UTC.
 
     Parameters
     ----------
     vals : int64 ndarray
-    tz1 : string / timezone object
-    to_utc : bint
+    tz1 : tzinfo
+    to_utc : bool
 
     Returns
     -------
@@ -430,7 +425,7 @@ cdef int64_t[:] _tz_convert_one_way(int64_t[:] vals, object tz, bint to_utc):
         Py_ssize_t i, n = len(vals)
         int64_t val
 
-    if not is_utc(get_timezone(tz)):
+    if not is_utc(tz):
         converted = np.empty(n, dtype=np.int64)
         if is_tzlocal(tz):
             for i in range(n):