Replace explicit z-level checks with defines

code/datums/antagonists/cult.dm

@@ -257,7 +257,7 @@
 	var/sanity = 0
 	while(summon_spots.len < SUMMON_POSSIBILITIES && sanity < 100)
 		var/area/summon = pick(GLOB.sortedAreas - summon_spots)
-		if(summon && (summon.z in GLOB.station_z_levels) && summon.valid_territory)
+		if(summon && is_station_level(summon.z) && summon.valid_territory)
 			summon_spots += summon
 		sanity++
 	update_explanation_text()

code/datums/antagonists/nukeop.dm

@@ -232,7 +232,7 @@
 
 /datum/team/nuclear/proc/syndies_escaped()
 	var/obj/docking_port/mobile/S = SSshuttle.getShuttle("syndicate")
-	return (S && (S.z == ZLEVEL_CENTCOM || S.z == ZLEVEL_TRANSIT))
+	return S && (is_centcom_level(S.z) || is_transit_level(S.z))
 
 /datum/team/nuclear/proc/get_result()
 	var/evacuation = SSshuttle.emergency.mode == SHUTTLE_ENDGAME

code/datums/diseases/advance/advance.dm

@@ -408,7 +408,7 @@
 			AD.Refresh()
 
 		for(var/mob/living/carbon/human/H in shuffle(GLOB.alive_mob_list))
-			if(!(H.z in GLOB.station_z_levels))
+			if(!is_station_level(H.z))
 				continue
 			if(!H.HasDisease(D))
 				H.ForceContractDisease(D)

code/datums/mind.dm

@@ -545,7 +545,7 @@
 				if(I == src)
 					continue
 				var/mob/M = I.current
-				if(M && (M.z in GLOB.station_z_levels) && !M.stat)
+				if(M && is_station_level(M.z) && !M.stat)
 					last_healthy_headrev = FALSE
 					break
 			text += "head | not mindshielded | <a href='?src=[REF(src)];revolution=clear'>employee</a> | <b>[last_healthy_headrev ? "<font color='red'>LAST </font> " : ""]HEADREV</b> | <a href='?src=[REF(src)];revolution=rev'>rev</a>"