Adding startup services
nz-icon-register.service.ts

import { APP_INITIALIZER, Injectable } from '@angular/core';
import { NzIconService } from 'ng-zorro-antd/icon';

export const SvgIcons = [
    // nzType='plus'
    {
        namespace: 'nz:plus',
        literal: '<svg viewBox="64 64 896 896" focusable="false" fill="currentColor" width="1em" height="1em" data-icon="plus" aria-hidden="true"><defs><style></style></defs><path d="M482 152h60q8 0 8 8v704q0 8-8 8h-60q-8 0-8-8V160q0-8 8-8z"></path><path d="M176 474h672q8 0 8 8v60q0 8-8 8H176q-8 0-8-8v-60q0-8 8-8z"></path></svg>',
    },
];

@Injectable({
    providedIn: 'root'
})
export class NzIconRegisterService {

    constructor(
        private nzIconService: NzIconService,
    ) { }

    registeIcons(): void {
        SvgIcons.forEach(icons => {
            this.nzIconService.addIconLiteral(icons.namespace, icons.literal);
        })
    }
}

function factory(service: NzIconRegisterService ) {
    return () => service.registeIcons(); 
}

export const ICON_REGISTER_PROVIDES = [
    NzIconRegisterService ,
    {
        provide: APP_INITIALIZER,
        useFactory: factory,
        deps: [ NzIconRegisterService ],
        multi: true,
    }
];

Add the startup service to the startup item
app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { NgModule } from '@angular/core';
import { ICON_REGISTER_PROVIDES } from '@core/services/nz-icon-register.service';

@NgModule({
  declarations: [AppComponent],

  imports: [
    AppRoutingModule,
    BrowserModule,
    HttpClientModule,
    // ...other modules
  ],
  providers: [
    ICON_REGISTER_PROVIDES,
  ],
  bootstrap: [AppComponent],
})
export class AppModule {}