<style>
.zeromap div,
.zeromap iframe {
width: 100% !important;
height: 100% !important;
border: none;
border-radius: 20px; /*радиус скругления углов*/
}
</style>
<iframe src="https://yandex.ru/map-widget/v1/?ll=30.308583%2C59.934529&mode=poi&poi%5Bpoint%5D=30.306125%2C59.934081&poi%5Buri%5D=ymapsbm1%3A%2F%2Forg%3Foid%3D157776064978&z=15.91&scroll=false" width="100%" height="100%" frameborder="1" allowfullscreen="true" style="position:relative;">
</iframe>