diff --git a/backend/gn_module_zh/geometry.py b/backend/gn_module_zh/geometry.py
index b3fb94bb..ef05fb40 100644
--- a/backend/gn_module_zh/geometry.py
+++ b/backend/gn_module_zh/geometry.py
@@ -14,48 +14,44 @@
 import pdb
 
 
-def set_geom(geometry, id_zh=None):
+def set_geom(geometry_geojson, id_zh=None):
     if not id_zh:
         id_zh = 0
+
+    geometry = func.ST_SetSRID(func.ST_GeomFromGeoJSON(str(geometry_geojson)), 4326)
     # SetSRID for POSTGIS < 3.0 compat
     # select only already existing ZH geometries which intersect with the new ZH geometry
     q_zh = DB.session.scalars(
         select(TZH)
         .where(
             func.ST_Intersects(
-                func.ST_GeogFromWKB(func.ST_AsEWKB(TZH.geom)),
-                func.ST_GeogFromWKB(func.ST_AsEWKB(func.ST_GeomFromGeoJSON(str(geometry)))),
+                TZH.geom,
+                geometry,
             )
         )
         .where(
             func.ST_Touches(
-                func.ST_GeomFromWKB(func.ST_AsEWKB(TZH.geom), 4326),
-                func.ST_GeomFromWKB(func.ST_AsEWKB(func.ST_GeomFromGeoJSON(str(geometry))), 4326),
+                TZH.geom,
+                geometry,
             )
             == False
         )
     ).all()
 
     is_intersected = False
-    polygon = DB.session.scalar(
-        select(func.ST_SetSRID(func.ST_GeomFromGeoJSON(str(geometry)), 4326))
-    )
+    polygon = geometry
     for zh in q_zh:
         if zh.id_zh != id_zh:
-            zh_geom = DB.session.scalar(select(func.ST_GeogFromWKB(func.ST_AsEWKB(zh.geom))))
-            polygon_geom = DB.session.scalar(
-                select(func.ST_GeogFromWKB(func.ST_AsEWKB(func.ST_GeomFromGeoJSON(str(geometry)))))
-            )
-            if DB.session.scalar(select(func.ST_Intersects(polygon_geom, zh_geom))):
+            if DB.session.scalar(select(func.ST_Intersects(polygon, zh.geom))):
                 if DB.session.scalar(
-                    select(func.ST_GeometryType(func.ST_Intersection(zh_geom, polygon_geom, 0.1)))
+                    select(func.ST_GeometryType(func.ST_Intersection(zh.geom, polygon, 0.1)))
                 ) not in ["ST_LineString", "ST_MultiLineString"]:
                     is_intersected = True
             if DB.session.scalar(
                 select(
                     func.ST_Contains(
-                        zh_geom,
-                        polygon_geom,
+                        zh.geom,
+                        polygon,
                     )
                 )
             ):
@@ -64,15 +60,15 @@ def set_geom(geometry, id_zh=None):
             if DB.session.scalar(
                 select(
                     func.ST_Contains(
-                        polygon_geom,
-                        zh_geom,
+                        polygon,
+                        zh.geom,
                     )
                 )
             ):
                 raise BadRequest("La ZH englobe complètement une ZH existante")
                 # TODO: not detected if contained entirely in 2 or more ZH polygons
 
-            polygon = DB.session.scalar(select(func.ST_Difference(polygon_geom, zh_geom)))
+            polygon = DB.session.scalar(select(func.ST_Difference(polygon, zh.geom)))
 
     return {"polygon": polygon, "is_intersected": is_intersected}