You can use this rule:
RewriteEngine On
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s/+(testing/mypage\.php)\?PropertyBuyRent=rent&Developer=&Resort=([^&]+)&City=&State=&Country=&Price= [NC]
RewriteRule ^ /%1/TimeshareForRent/%2? [R=301,L,NE]
RewriteRule ^(testing/mypage.php)/TimeshareForRent/([^/]+)/?$ /$1?PropertyBuyRent=rent&Developer=&Resort=$2&City=&State=&Country=&Price= [L,NC,QSA]