Go to Zoomsounds > Settings > Appearance and in Extra CSS enter

.next-btn .svg-icon, .prev-btn .svg-icon{
  display: none;
}
.next-btn:after, .prev-btn:after{
  content: "";
  display: block;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate3d(-50%, -50%, 0);
  width: 15px;
  height: 15px;
  background-size: contain;
  background-position: 50% 50%;
  background-image: url(data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiA/PjwhRE9DVFlQRSBzdmcgIFBVQkxJQyAnLS8vVzNDLy9EVEQgU1ZHIDEuMS8vRU4nICAnaHR0cDovL3d3dy53My5vcmcvR3JhcGhpY3MvU1ZHLzEuMS9EVEQvc3ZnMTEuZHRkJz48c3ZnIGVuYWJsZS1iYWNrZ3JvdW5kPSJuZXcgMCAwIDk2IDk2IiBoZWlnaHQ9Ijk2cHgiIGlkPSJhcnJvd19yaWdodCIgdmVyc2lvbj0iMS4xIiB2aWV3Qm94PSIwIDAgOTYgOTYiIHdpZHRoPSI5NnB4IiB4bWw6c3BhY2U9InByZXNlcnZlIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHhtbG5zOnhsaW5rPSJodHRwOi8vd3d3LnczLm9yZy8xOTk5L3hsaW5rIj48cGF0aCBmaWxsPSIjZmZmZmZmIiBkPSJNMTIsNTJoNjIuMzQ0TDUyLjg4OCw3My40NTZjLTEuNTYyLDEuNTYyLTEuNTYyLDQuMDk1LTAuMDAxLDUuNjU2YzEuNTYyLDEuNTYyLDQuMDk2LDEuNTYyLDUuNjU4LDBsMjguMjgzLTI4LjI4NGwwLDAgIGMwLjE4Ni0wLjE4NiwwLjM1Mi0wLjM5MSwwLjQ5OC0wLjYwOWMwLjA2Ny0wLjEwMSwwLjExNC0wLjIxLDAuMTcyLTAuMzE1YzAuMDY2LTAuMTI0LDAuMTQyLTAuMjQyLDAuMTk1LTAuMzczICBjMC4wNTctMC4xMzUsMC4wODktMC4yNzUsMC4xMjktMC40MTVjMC4wMzMtMC4xMTEsMC4wNzYtMC4yMTcsMC4wOTktMC4zMzFDODcuOTczLDQ4LjUyNSw4OCw0OC4yNjMsODgsNDhsMCwwICBjMC0wLjAwMy0wLjAwMS0wLjAwNi0wLjAwMS0wLjAwOWMtMC4wMDEtMC4yNTktMC4wMjctMC41MTktMC4wNzgtMC43NzRjLTAuMDI0LTAuMTItMC4wNjktMC4yMzEtMC4xMDQtMC4zNDkgIGMtMC4wMzktMC4xMzMtMC4wNjktMC4yNjgtMC4xMjMtMC4zOTdjLTAuMDU4LTAuMTM5LTAuMTM2LTAuMjY1LTAuMjA4LTAuMzk2Yy0wLjA1NC0wLjA5OC0wLjA5Ny0wLjE5OC0wLjE1OS0wLjI5MiAgYy0wLjE0Ni0wLjIyMS0wLjMxNC0wLjQyNy0wLjUwMS0wLjYxNEw1OC41NDQsMTYuODg4Yy0xLjU2Mi0xLjU2Mi00LjA5NS0xLjU2Mi01LjY1Ny0wLjAwMWMtMS41NjIsMS41NjItMS41NjIsNC4wOTUsMCw1LjY1OCAgTDc0LjM0Myw0NEwxMiw0NGMtMi4yMDksMC00LDEuNzkxLTQsNEM4LDUwLjIwOSw5Ljc5MSw1MiwxMiw1MnoiLz48L3N2Zz4=);
}
.prev-btn:after{
  background-image: url(data:image/svg+xml;base64,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);;
 }

you can have any icons by converting svgs via this site